I have a touchscreen Chromebook and it has had this issue with Proxmox for a long time. The workaround is to click & drag the gray bars in between the sections. Weirdly, the latest Chrome browser on Windows does not have this issue. Also, there used to be a setting in chrome://flags to turn off certain touch UI features and that fixed this but Google removed that flag a few versions ago.
If your Chromebook is a detachable or a convertible, it won't scroll at all in tablet mode other than by using the mobile version of the UI which has less functionality.
