How about showing the issue?

1) Why in Firefox when a video is played in full screen the tab is moved to the right where sign + new tab 2) After updating to a new version, the speaker icon disappears on the tabs in which the audio or video was playing, it becomes visible only when you hover over it with the mouse pointer. this is very annoying

See also the answer I posted in your other thread.

• /questions/1348060 tabs moving to the right after ESC from Full Screen, and speaker icon disappearing

That is probably expected behavior because the normal screen needs to be regenerated if you exit full screen and the the Tab bar gets reset causing too right align the tabs (previous context isn't stored).
You may also have that many tabs that there are no scroll buttons in Full Screen Mode but there are in normal mode.

This is affected by the Density settings as selected on the Customize page.

• in Compact mode you only see the sound playing icon and not the website favicon
• in Normal mode you see the favicon by default and the sound playing icon on hover
  there is a secondary line that shows the 'playing' or 'muted' state since the icon is hidden by default

but this problem does not appear on Google Chrome or other browsers