User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:75.0) Gecko/20100101 Firefox/75.0

Steps to reproduce:

Working on Windows 10 in a Remote Desktop session, having several dozen tabs open in Firefox.
Reproducibility 100%.

Actual results:

Height of the "List all tabs" list is not adjusted accordingly and thus one or two last entries are hidden behind the Windows taskbar on the screen bottom.

Expected results:

Without Remote Desktop height is OK and all items are visible.

Hi Tomas, I tried to reproduce this issue by remote conecting to a laptop with 1080p resolution and the "list all tabs" drop down cuts right before it reaches the bottom where the user can scroll through and see all opened tabs.

Can you please try this with a fresh new profile on that machine you are connecting to ? you can find the steps here :
https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles?redirectlocale=en-US&redirectslug=Managing-profiles#w_starting-the-profile-manager

Also can you please install our Nightly version on that machine ? you can find the link here : https://nightly.mozilla.org/

Does this issue occur if you remote connect to a different machine ?

Reproducible the same way using a new profile and also using Nightly 78.0a1 (2020-05-05) (64-bit).

The machine I am connecting my Remote Desktop from is a notebook (1920x1080, scaling 150%). The machine I am connecting to is a desktop with a bigger screen. When connecting Remote Desktop I can see Windows changing resolution of the remote screen and all apps are adjusting dynamically. I suspect Firefox does not react to this change completely ok. (You might be able to achieve a similar situation by simply adjusting your screen resolution locally?)

I have no other machine to try this on right now...

I was unable to reproduce this issue, but I will set a component for it and maybe one of our devs can take a look and might be able to reproduce it on his end.

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is -- (non,) indicating it has has not been previously triaged, the bug's Severity is being updated to -- (default, untriaged.)

It also happens, if you resize the taskbar (make it bigger).

STR:

1. Right-click on the taskbar and uncheck "Lock the taskbar" (so you can resize the taskbar)
2. Resize the taskbar with your mouse, to make it bigger
3. Click on the all tabs button

Yep, I was able to reproduce the issue if I resized my taskbar, I think its suppose to adjust the size of the dropdown list in real time according to the taskbar itself ? but on my end it only adjusts once I restart Firefox.
This does not happen only when I try to remote connect to a different machine, the same thing happens on the machine I am on as well.

Should this block 1494755?

Nothing, just b(u/e)gging you for a fix :)

Can anyone test if this is still reproducible?
I think this has been fixed by bug 1746774.

Can not reproduce the problem anymore using Firefox 108.0.1 on Windows 10.
Thanks a lot!

Marking this issue Verified based on Comment 11, Thank you Tomas for verifying this issue on your end.