Support ID-fields in "convert to subtask" action

I was really enthusiastic to start using ID fields for a process, as one of the steps involves converting a task to a subtask, where the new parent task is to be picked from many tasks that all have the same name. (It’s from our main project template)

I thought I’d make this easier by adding an ID-field, as the ID-field seemed to be intended to make refering to the correct task easier.

When choosing “convert to subtask” I found typing the exact ID-field didn’t produce any hits.