View grouping in the thumbnails sidebar

[lrecknagel]

Description

When a project has plenty of views, the sidebar of thumbnails gets messy, and it's difficult to keep the orientation there.
To improve this, I would like to see some kind of lightweight approach to enable grouping of views in the sidebar.

This can be, for example, via the properties child element of views.

Priority

I'm willing to add this feature myself and raise a PR (please confirm approach first)

More information

No response