I forgot to mention that I started Firefox in troubleshoot mode, and the bookmarks were missing there too. I also didn't mention that in the bookmarks toolbar folder in the bookmarks menu, all of my bookmarks are present. So I know they aren't lost, just missing from the toolbar.

Why can't we edit our original post indefinitely like we can replies? I was able to edit this reply two days after it was posted when I couldn't edit my original post two minutes after posting it. If I could have edited my original post, it wouldn't have been necessary to post a reply to it to add more information.

If you go into the Customize panel, is there an item at the left end of the Bookmarks Toolbar called "Bookmarks Toolbar Items"? See:

Customize Firefox controls, buttons and toolbars

Wherever that is usually is where Firefox will show the bookmarks. If it fell off the bar, hmm, can you see it in the box of available controls, or on another bar?

If it's nowhere to be found, try the "Restore Defaults" button at the bottom of the panel to restore the original toolbar layout.

I added the "bookmarks toolbar items" to the menu bar when this first occurred as a temporary fix, but all of my bookmarks were present as the attachment shows. This was instead of just an icon like it used to be that looked like an open book. It was an icon that's quite similar to what is now the "show sidebar" icon, and now that I think about it, it was this exact same icon, and it did the exact same thing.

Now I've done it, I was trying to see if I could move the sidebar icon to the menu bar, (I couldn't), so then I added it to the overflow menu, but I didn't like it there. I then removed it from the overflow menu and now it's disappeared also. I can't get it back as there is no option in settings to enable sidebar to be able to add the icon again. Oh well, it's back to adding the bookmarks toolbar items to the menu bar. At least they're just one click away.

I know I've seen it before, but I can't find restore defaults, and I don't know if that would help reinstalling the sidebar icon when it was needed if my bookmarks didn't reappear in the bookmarks toolbar.

Thanks for the help, I should have left it alone.

If you don't have other controls on the Bookmarks Toolbar, the Bookmarks Toolbar Items should occupy the full width there.

The Sidebars button changed appearance recently. Can you find this new one?

I don't see "other controls" anywhere, and I'm not sure where I would find it. I've attached a screenshot of the menu items I see when I left click, (right click for people who use their mouse with their right hand), so that you can see what I have. I found the sidebar button, it was next to the three bar menu button. It was on the left side of the panel earlier before I tried to move it next to the password key on the menu bar, but that's when I messed up things and it disappeared. Or at least I thought it did, so now it's on the right end, which may have been where it was when I thought I lost it. It's appearance is different than those in your examples, the shaded section on your example is narrower that than what I have, and mine has lines representing, if I'm not mistaken, sentences in a book. I don't know how to move it back to the left side as there's only options to pin it to overflow and remove it from the toolbar, but I don't know if it really matters where it is, it's just more accessible on the left side.

The overflow menu is where the two chevrons would be on the right end the bookmarks toolbar if it was full, correct? The bookmarks toolbar is where my bookmarks used to be, but you can see it's completely empty.

Out of curiosity I accessed Firefox on my wife's desktop to check it out, and my bookmarks were all present on the bookmarks toolbar. I wasn't signed in to Firefox for it to sync, so to avoid losing my bookmarks I didn't sign in. I'm wondering if I sign out of Firefox on my computer, then sign in to Firefox and enable sync on her computer, then sign back in on my computer, if it will sync Firefox on my computer to what's on on my wife's computer? That would solve my problem, and it's not like I use her computer often, just when I need to compare something on hers to what I have on mine.

Unfortunately, you cannot use Sync to rearrange your toolbars, that is a local configuration.

You have the older style Sidebar button, which is fine. Go back to the Customize panel and you can drag the button back to the left side if you prefer.

Meanwhile, also try placing "Bookmarks Toolbar Items" at the left end of the Bookmarks Toolbar. (In a previous screenshot, you had it on the menu bar, but right now, I don't see it anywhere.)

Wow! So simple yet not so simple. I tried moving it to the left side, but I wasn't on the Customize Firefox screen, so it obviously wasn't going to work.

I just remembered that when I was on my wife's computer the bookmarks button was a star with a bracket underneath it, so I was mistaken in thinking the The Sidebar button is what the bookmarks button used to look like. Although the star with a bracket underneath it was just a button like the key is for passwords. When I had the scrolling issue in the bookmarks menu, I put the Bookmarks button on the top next to the password button, and when I clicked on it, it opened the sidebar just like the Sidebar button does now. Once I found out that I could have the Bookmarks Toolbar open in the sidebar all the time, I removed the Bookmarks Toolbar Items from Firefox and only used the sidebar button. I only put the Bookmarks Toolbar Items back on top to take the screenshot.

Thanks again for all your help!