For any program 'Full Screen' is Full Screen and Task bar is always not visible.

On Windows 11, I can use 'F11' key to go to full screen and use again to come out of Full Screen.

At the top of each window that is not full screen, there are three icons on top right. The one in the middle is 'maximise' Use that option to 'maximise' the window so it uses all the desktop, but it does not cover the Task Bar.

I presume you have a Thunderbird shortcut icon on desktop. Check it has correct settings.

• Right click on desktop Thunderbird icon and select 'Properties'
• In the 'Shortcut' tab
• Run: ideally set at 'Normal Window' as it gives you options after starting OR if you always want it maximised then select 'Maximised'
• Click on 'Apply' and click on 'OK'

I meant maximized not full screen. Edited the question.

I said in initial post that minimizing and maximizing resolve the problem. Also in Firefox pressing F11 two times.

Changing run settings: normal, minimized, maximized does nothing. For you setting the shortcut to run in different modes changes anything in start behavior of Thunderbird?

The question is how to not overlap hidden taskbar when Thunderbird and Firefox start maximized? If the taskbar is not hidden then Thunderbird do not overlap. Is happening only when the taskbar is set to hide. Same problem happens to Firefox.

Thanks for further info. I'm with you now : )

If Thunderbird is 'maximised' AND you have the Task Bar set up to auto hide then Thunderbird appears to look similar to 'Full Screen'. This is normal view in Windows 11 when a window is maximised and TaskBar is set as hidden.

But what if you then want to see the TaskBar without altering anything with Thunderbird? The Windows OS requires you to: Hover mouse cursor over very bottom edge of screen and the Task Bar reappears temporarily and remains visible whilst mouse hovers over it.

re :For you setting the shortcut to run in different modes changes anything in start behavior of Thunderbird?

Yes. If Run: 'maximised' Then Thunderbird starts up with a maximised window using all available screen.

If Run: 'minimised' Then Thunderbird will start as 'minimised' and display icon on TaskBar. If I need to then use it, a click on that icon on TaskBar will show the Thunderbird window.

If Run: Normal Window Then Thunderbird will start up in a window of height and width set by me. It might look like it filles the whole screen if that was something previously set up, but the difference is that I can hover over the side edge or top edge, cursor changes to a double head arrow, left click-hold down and then drag the edge to a suitable size. Eg: Window now uses about half the screen size. That means if I maximise using the middle icon, it fills screen and then I can use the same middle icon to 'Restore down' back to normal window size.

Really I think you do not understand the question.

Problem is exactly that hovering the cursor over the bottom of screen do not show hided taskbar when Thunderbird and Firefox start maximized. Recently I found that this problem also appears when snap to maximize. Edge for example and other applications started maximized it wont overlap the hided taskbar.

Weird that for you setting the shortcut to start Thunderbird minimized works. For me and many others who use Thunderbird do not work and need to use an add-on to do this.

Anyway the question remains. How to not overlap hidden taskbar when Thunderbird and Firefox start maximized?