I absolutely don't need those two rightmost elements! The previous version didn't have them, or they were deleted. Now all the windows are moving apart, and even if you set the minimum width of these unnecessary elements, they take up space on the screen in vain.
You did not include your plugin list when you pasted in your desktop info. It looks like you will have to disable or delete the plugins you have added that have created those extra panes / elements.
I would suggest just disabling them one by one and see when the additional UI panels disappear. Also, just a sidenote, but having so many plugins installed will definitely have performance impact, especially on the amount of RAM used by Joplin.
Oops! I completely forgot about the plugins - everything worked so smoothly for more than a year, until the server database was helped to collapse.. However. I just disabled all the plugins at once, updated them, and gradually started enabling them. The initial situation did not happen again - everything works well, except for one NEW thing - suddenly Joplin takes all the memory and slows down like hell.
For now, I'll be looking for which plugin is interfering with normal operation.