Allow task manager to have children (#6771)

* Initial commit

Forked at: 19c1d902
Parent branch: origin/master

* WIP

Forked at: 19c1d902
Parent branch: origin/master

* WIP

Forked at: 19c1d902
Parent branch: origin/master

* WIP

Forked at: 19c1d902
Parent branch: origin/master

* WIP

Forked at: 19c1d902
Parent branch: origin/master

* WIP

Forked at: 19c1d902
Parent branch: origin/master

* WIP

Forked at: 19c1d902
Parent branch: origin/master

* changelog

* Remove Box

* Make future nicer

* Revert "Make future nicer"

This reverts commit 49fb8fb6

.

* Simplify

* Additional check

* Simplify more

Co-authored-by: Bastian Köcher <[email protected]>