docs: Improve readability of columns in Quick Reference (#830)

By separating Sort and Group in to different columns, it is
easier to spot the gaps in functionality.

This required combing the Filter and Presence/Absence columns instead
in to a single Filters column.

Author: claremacrae

docs/quick-reference/index.md

@@ -14,26 +14,26 @@ has_toc: false
 
 This table summarizes the filters and other options available inside a `tasks` block.
 
-| [Filter][1]                                                                        | Presence<br>Absence                          | [Sort][2]<br>[Group][3]                     | [Display][4]           |
-| ---------------------------------------------------------------------------------- | -------------------------------------------- | ------------------------------------------- | ---------------------- |
-| `done`<br>`not done`                                                               |                                              | `sort by status`<br>`group by status`       |                        |
-| `done (before, after, on) <date>`                                                  | `has done date`<br>`no  done date`           | `sort by done`<br>`group by done`           | `hide done date`       |
-| `starts (before, after, on) <date>`                                                | `has start date`<br>`no  start date`         | `sort by start`<br>`group by start`         | `hide start date`      |
-| `scheduled (before, after, on) <date>`                                             | `has scheduled date`<br>`no  scheduled date` | `sort by scheduled`<br>`group by scheduled` | `hide scheduled date`  |
-| `due (before, after, on) <date>`                                                   | `has due date`<br>`no  due date`             | `sort by due`<br>`group by due`             | `hide due date`        |
-| `happens (before, after, on) <date>`                                               | `has happens date`<br>`no  happens date`     |                                             |                        |
-| `is recurring`<br>`is not recurring`                                               |                                              |                                             | `hide recurrence rule` |
-| `priority is (above, below)? (low, none, medium, high)`                            |                                              | `sort by priority`                          | `hide priority`        |
-|                                                                                    |                                              | `sort by urgency`                           |                        |
-| `path (includes, does not include) <path>`                                         |                                              | `sort by path`<br>`group by path`           |                        |
-|                                                                                    |                                              | `group by folder`                           |                        |
-|                                                                                    |                                              | `group by filename`                         |                        |
-| `heading (includes, does not include) <string>`                                    |                                              | `group by heading`                          |                        |
-|                                                                                    |                                              | `group by backlink`                         | `hide backlink`        |
-| `description (includes, does not include) <string>`                                |                                              | `sort by description`                       |                        |
-| `tag (includes, does not include) <tag>`<br>`tags (include, do not include) <tag>` |                                              | `sort by tag`<br>`sort by tag <tag_number>` |                        |
-| `exclude sub-items`                                                                |                                              |                                             |                        |
-| `limit to <number> tasks`<br>`limit <number>`                                      |                                              |                                             |                        |
+| [Filters][1]                                                                           | [Sort][2]                                   |  [Group][3]         | [Display][4]           |
+| ---------------------------------------------------------------------------------------| ------------------------------------------- | --------------------| -----------------------|
+| `done`<br>`not done`                                                                   | `sort by status`                            | `group by status`   |                        |
+| `done (before, after, on) <date>`<br>`has done date`<br>`no  done date`                | `sort by done`                              | `group by done`     | `hide done date`       |
+| `starts (before, after, on) <date>`<br>`has start date`<br>`no  start date`            | `sort by start`                             | `group by start`    | `hide start date`      |
+| `scheduled (before, after, on) <date>`<br>`has scheduled date`<br>`no  scheduled date` | `sort by scheduled`                         | `group by scheduled`| `hide scheduled date`  |
+| `due (before, after, on) <date>`<br>`has due date`<br>`no  due date`                   | `sort by due`                               | `group by due`      | `hide due date`        |
+| `happens (before, after, on) <date>`<br>`has happens date`<br>`no  happens date`       |                                             |                     |                        |
+| `is recurring`<br>`is not recurring`                                                   |                                             |                     | `hide recurrence rule` |
+| `priority is (above, below)? (low, none, medium, high)`                                | `sort by priority`                          |                     | `hide priority`        |
+|                                                                                        | `sort by urgency`                           |                     |                        |
+| `path (includes, does not include) <path>`                                             | `sort by path`                              | `group by path`     |                        |
+|                                                                                        |                                             | `group by folder`   |                        |
+|                                                                                        |                                             | `group by filename` |                        |
+| `heading (includes, does not include) <string>`                                        |                                             | `group by heading`  |                        |
+|                                                                                        |                                             | `group by backlink` | `hide backlink`        |
+| `description (includes, does not include) <string>`                                    | `sort by description`                       |                     |                        |
+| `tag (includes, does not include) <tag>`<br>`tags (include, do not include) <tag>`     | `sort by tag`<br>`sort by tag <tag_number>` |                     |                        |
+| `exclude sub-items`                                                                    |                                             |                     |                        |
+| `limit to <number> tasks`<br>`limit <number>`                                          |                                             |                     |                        |
 
 Other layout options: