If many extension, then panel board with btns is not in center but on left that made disonanse

[ManPython]

Describe the bug
If many extension, then panel board with btns is not in center but on left that made disonanse

To Reproduce
Steps to reproduce the behavior:

Expected behavior
It should be in center, or give option for whole wide size width as screen allow.

Screenshots

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser \ FF 109.0.1
• Version [e.g. 22]

Additional context
Add any other context about the problem here.

[ManPython]

Table of Contents (2) is suspected here.

[ManPython]

Also take point about separation row as 1st and 2nd with icons, there are to close and looks ugly when many
jupyterlab/jupyterlab#13957
https://user-images.githubusercontent.com/25403861/217939295-852bfb4f-8bb1-466e-ac6b-da6951f1a5cf.png

[RRosio]

@ManPython thank you for opening this issue! As Notebook 6.5.x will be pulling it's static assets from NbClassic, I've copied this issue to the NbClassic repository so that this enhancement can be addressed there. This is the new issue in NbClassic.