Firefox loses icons in toolbar when new tab is opened
 

For some time I have had an intermittent problem with Firefox: when I open a new tab it no longer shows the icons I have placed in the toolbar--most importantly, the bookmarks.
When I open "Customize" I don't seem to need to anything--they simply reappear in the tabs I have opened.
This has been happening from time to time over the last few months, over more than one computer and various installations of Mint 18.3 and Mint 19, and of course several updates.
Is there a fix?

I've had a problem for a wee while with Firefox that sometimes the address bar extends to the right hand side of the page, meaning that the search bar and icons ("View history...", "Show sidebars", NoScript, uBlock Origin etc.) are not displayed. I am able to rectify this by selecting View->Toolbars->Customise and then hitting Esc. Are we talking about the same thing here?

If so, I would also like to know what causes this and whether or not there is a fix!

I think we are talking about the same thing: although for me the address bar does not quite reach the edge of the page; the icons for "more tools" and "Menu" are still showing. As soon as I open Menu>Customize the missing icons reappear; once Customize has opened I don't actually need to perform any actions.

Yup. I only hit Esc at the Customise window to get rid of the window again.

I've been looking at a potential CSS solution that would set a maximum size for the address bar. Not perfect as different values would have to be used for different resolutions, but a new Firefox version, 63.0.3, came down the pipes a few days ago and I haven't seen the issue occur since then. In the off-chance that this version has solved the problem, I'm going to wait until it occurs again before working any more on this.

Hi Brant. The problem occurred again today when I opened up Firefox after resuming my laptop from sleep. I've tried to replicate it but in vain.

So, for the moment, I've set the address bar to a fixed width to see if that makes any difference.

Edit/create the file ~/.mozilla/firefox/<profile name>.default/chrome/userChrome.css and populate it with:

then restart Firefox.

Change the width depending on your screen resolution. I'm using 1366x768.

You might want to try this and see if this resolves the issue. I'll let you know how it goes at my end.

I would be curious to know how common this problem is. I know for me it has existed in the last few editions of Firefox.

FWIW, I've never seen this problem here or on my Windows box. One thing I've done, however, is move the Home button to just after the Search box, so that may affect how the toolbar works.
My toolbar:
Back Next Address Reload Search Home Download...various button far right (and right-aligned) as add-ons create them.

I am not sure if this was caused by the latest Firefox update, but since the update this problem is constant. I have not tried modifying it yet.

On the other hand, I haven't experienced the problem again since adding the setting in my post above.

I thought scasey's suggestion (see post above) was elegant. I moved the Home icon, and, so far, the problem has not showed itself. On the other hand, I keep hitting Home by mistake!
I'll call this solved (although I still find it a funny bug).
Thanks everyone!

I do that because some previous version change moved the Home somewhere else, and my mouse expects it to be there. I also have the download icon there, for the same reason. You could probably put anything there with the same effect.

And Thank You. I don't often get "elegant" about much of anything these days. :)

Aand. . .I've marked it unsolved.
I still think the answer was elegantly simple, but the problem repeated this morning. Sigh.

Have you tried my solution above? I haven't seen the problem re-occur since I adopted it.