Delete Subtasks at once

[Der-K-2000]

Is your feature request related to a problem? Please describe.

At the bottom of a task list you can load closed/finished tasks and after that it's possible to delete those tasks at once.

But I'm wondering why there is no similar function for subtasks.

Describe the solution you'd like

Bulk-delete of closed/finished subtasks

Describe alternatives you've considered

No response

Additional context

No response