Would be nice if we can modify tab context menu in the same way that the main context menu (via an .xml file, even using the same contextMenu.xml file) or other way.

After merge #12150 it's possible that not everyone will be happy to move some items to an additional sub-menu. First unhappy report #12098 (comment).

Temporary solution:
Now most (if not all) commands from the tab context menu are generally available, so they can be placed in the main context menu (and this menu we can modify as we want via contextMenu.xml file).