Additional Lists

Put a task on more than one list. Get Lists For A Task returns the home list and any additional lists. Add / Remove manage non-home membership. Move Task changes the home list.

📄️Get Lists For A Task

Returns every list the task belongs to. The home list is the one with `isHome: true` (same id as `properties.primaryListId`). Other rows are additional lists. Move Task (`PUT .../home-list`) changes the home list.

📄️Add A Task To An Additional List

Adds an existing task to this list as an additional (non-home) membership. `POST` is not idempotent — adding a task that is already on the list conflicts. Response: `{ 'success': true }`. This path does not delete the task. Delete the task with `DELETE /projects/tasks/{taskId}`. Use Move Task to change the home list.

📄️Remove A Task From Additional List

Removes an additional-list membership. Response: `{ 'success': true }`. Cannot remove the task’s home list — move the home list first. This does not delete the task.

📄️Move Task

Moves the task’s home list to another list. Response: `{ 'success': true }`. **409** has two causes and one status: the task is already on the destination list (including as an additional list), or it is not on the current home list. If it is already an additional member of the destination, `DELETE /projects/lists/{listId}/tasks/{taskId}` on that list, then call Move Task. There is no separate error code for the two causes.