Main UI: Can't pin left side bar

Openhab 3.2
Raspberry Pi 3
Openhab-UI: xxx.xxx.xxx.xxx:8080
Browser: Firefox
Remote Computer: Ubuntu 20.04

When I click on the pin icon on the top right of the left side bar, I see that the pin icon changes from disabled to enabled. However, the side bar slides back no matter if the pin is enabled or disabled (crossed out).

In the Chrome browser, I don’t see the pin at all.

Is there a solution for this or is this feature not implemented at all?.

I am working with a MacBookPro 13" with Ubuntu, (Screen Resolution 2560 x 1600).

In Firefox I have set the default zoom level at 133% and this is apparently exactly the point where openHAB draws the line between a narrow and normal screen. If I zoom in, the pin symbol disappears. If I zoom out, the pin function works as expected.
See also: