When you have a very large notebook, accessing tabs or rearranging tabs is a huge pain. The idea here would be to add several functionalities that would help improve this process. Specifically:
Allow tabs to be sorted along the bottom into groups
Include the below functions for the tab groups
Add in right click options to move tabs around. The following are just first thoughts on the most useful forms: "Move Tab to the last position", "Move Tab to First position", "Move tab left/right by 1", "Move tab left/right by 5"