dropdownpage scrollable and disappear on click (only)

[virk]

Is your feature request related to a problem? Please describe.
I try to introduce the dropdownpage as a possible place for the indexmenu. The current problem is, that as soon as I want to navigate through the namespaces in order to go to a certain namespace, the dropdownpage is closed on the first click. Additionally the dropdownpage does not seem scrollable, so the content of the indexmenu sometimes is not available at the bottom, if the index is opened/widend.

Describe the solution you'd like
A solution could be that the dropdownpage opens just on mouse over but remains opens until I move the mouse out of the dropdownpage again.
The advantage would be that the indexmenu is not required to be in the sidebar, where it (only) takes space most of the time, while it is not needed. It would just open in the dropdownpage, you can guide to and mouse-click your desired namespace.

Describe alternatives you've considered
Currently we have the indexmenu in the overlay plugin, which is better for us than in the sidebar, but having it in the dropdownpage would even improve usability.