Ability to collapse multi-level menus in the Menu editor

[atomicjack]

When creating large menu structures in the Appearance > Menu editor, it can be very overwhelming when there's a number of top-level items with child items... almost becoming an eyesore and confusingly difficult to navigate.

Could we work to make any menu item within the editor have the ability to be collapsed? Along with the default state upon loading the editor to have them collapsed, with an icon to expand it.

[punit5658]

I like to work on this ticket. To achieve solution to reduce parent - child menu tree. I have suggestion to add one icon i.e. ( + ) and ( - ) for small. We can change icon if any suggestion. By click on icon child menu will be hidden and get back visible on click again replace icon at same place.
Let me know if anyone can have more option.

One more improvement suggestion is : we can add like option icon which is contain multiple icons i.e. collapse/expand, show/hide ( here show hide can help immediate hide menu from menubar by adding class in frontend, no need to create multiple menu for single change ). Give me feedback for second option.

[adamsilverstein]

Let me know if anyone can have more option.

one other option would be a triangle that rotates when you click on it, similar to what we show when you open/close a widget section. maybe some mock ups here would help visualize what we are going for.