Add option to collapse children rows

[AMBudnik]

Description

I have been asked two times is there an option like collapseAll() for children rows (2+ levels of nesting) while using nestedRows functionality. We should consider adding this possibility.

Clients in many cases are using more than one level of nesting lie the one below

and it might be hard to organize such a long list if we do not hide children on initialization.

Your environment

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Inform forum

Related #6455

[AMBudnik]

We should also consider adding an option to collapse rows on load (in the initialization).

[AMBudnik]

I'm moving this topic to Github Discussions. And I welcome everyone to discuss this functionality and share your feedback.
See you there!