Add optional behavior [Alt] + [Click] to fully collapse/expand an OdinMenuTree.

[Romain Pechot]

When clicking on a foldout inside a tree view in Unity with LeftAlt or AltGr hold down it will completely expand or collapse all the sub-foldout.

Unity TreeView (Collapsed)

Unity TreeView (Mouse Click, one depth level expanded)

Unity TreeView (Alt + Mouse Click, full depth level expanded)

It would be nice to have this behavior in OdinMenuTree (this info could be store inside the OdinMenuTreeDrawingConfig).

[Romain Pechot]

Edit: formatting.