@mckaragoz FYI, this implements multiselection like you suggested. Is it OK that the nesting items are not selectable themselves in multiselection or what do you say?

Having the nesting items selectable would be a big help to easily to select al sub-items,
provided there's a checkbox on the nested item.

Ok, makes sense. Interestingly in the current implementation (single-selection only) it is impossible to select a nested list item. If you click it, it just toggles expansion.

So I guess the best way would be to add Selectable to the items. If it is set, the nested item can be selected by a body click in single-selection as well as multiselection and can only be expanded by a click on the expand button. If unset, it behaves as before.

We may leave it at nesting items being only for nesting/grouping, not selection. Neither Vuetify nor MUI have such functionality, and I guess for good reason.

If you look at MUI there are a couple of cool things a list can do, such as show the checkboxes either left or right, or show a switch instead of checkboxes.

The most promising way to implement all these things (as well as tri-state checkboxes for selecting on/off all nested items) would be to implement special list items, i.e. a MudListSwitchActionItem. That's gonna be a project for a future PR though.

Codecov Report

Attention: Patch coverage is 82.02247% with 16 lines in your changes are missing coverage. Please review.

Project coverage is 90.02%. Comparing base (28bc599) to head (02a1bc7).
Report is 126 commits behind head on dev.

@@            Coverage Diff             @@
##              dev    #8775      +/-   ##
==========================================
+ Coverage   89.82%   90.02%   +0.19%     
==========================================
  Files         412      421       +9     
  Lines       11878    12286     +408     
  Branches     2364     2437      +73     
==========================================
+ Hits        10670    11061     +391     
+ Misses        681      671      -10     
- Partials      527      554      +27     

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@ScarletKuro do you still want to review this?

added to v7.0.0 Migration Guide #8447