I'm not sure if you are referring to a sidebar, i.e., the Firefox sidebar or a sidebar in the web page itself?

The Firefox sidebar (for example, Ctrl+B for Bookmarks) generally is persistent. It can be resized by dragging the edge of it (this involves some very precise mouse pointer positioning to find the spot where you can click and drag).

Web page sidebars may appear/disappear based on either resolution or preferences. To test whether resolution is the issue, try zooming out one or two ticks (hold Ctrl and tap the - key) to see whether the page layout switches.

If it's not a responsive layout that switching the sidebar appearance automatically, you may need to find an icon or checkbox to "pin" the sidebar open.

Thanks for your reply. What I have is a slide bar. I don't know how to better describe it. If I am viewing an options chain and I want to scroll up or down there is in windows 10 a scroll bar, maybe a better description, about 1/4" showing. On the windows 11 laptop it is not there until the cursor moves over it and then it is ti thin to use efficiently use. Hope this is a better explanation. Thanks again.

Oh, got it. Let's call it a scroll bar. In the Windows 11 search box (on the Start menu or Taskbar) type scroll bar and look for something similar to "Automatically hide scroll bars in Windows". Click that to open a control panel so you can switch off that setting.

Alternately, there might be a way to set Firefox to ignore the system setting (if you like the invisible/hover scroll bar on other applications), but I'm still on Windows 10 so I haven't experimented.

Awesome!! Thanks so much. That solved the problem. I can't tell you how much I appreciate your help. You were so kind to give of your time. Thanks again. Hoyt