a82f3a0fe0
This adds unobtrusive tab button for selecting displayed tabs to the tabs region. The idea is, that this way, the filter is much more discoverable than it being hidden in options popover. The button is grayed out, when all tabs are visible. To only draw arrow, is achieved by setting `UILayout.emboss` to `NONE` or `NONE_OR_STATUS` Pull Request: https://projects.blender.org/blender/blender/pulls/135132