HI, the sidebar should be visible or invisible, no partly visible. If it is something has gone wrong with the code. Let us know if need help. A screenshot of partly visible would be great so we can tell if is broken or not https://support.mozilla.org/en-US/kb/firefox-screenshots

You can do this for clickable instead of going deep into the menu : https://support.mozilla.org/en-US/kb/firefox-sidebar-access-bookmarks-history-social

Please let us know if this solved your issue or if need further assistance.

I think you misunderstood what I was asking. The sidebar's width is adjustable. However, its width cannot be shrunk beyond a certain amount, leaving it partially visible. It can also be completely closed by clicking the "X" control button on its upper right; but closing it like this then requires that it be opened with the menu or with the key combination "Ctrl+B". It would be preferable, in my opinion, if I could minimize the width of the sidebar with an arrow control button, which remained visible so that I could then click it again to reopen the sidebar to its previous width. Thus, the sidebar would appear to retract completely if I so choose to use it this way. Therefore, I would not have to use multiple steps or keys to accomplish this task.