The Close Tabs Shortcuts add-on doesn't define a toolbar button, it just sets up keyboard shortcuts.

Generally speaking, the add-ons which have grayed text and appear at the bottom of the Extensions drop-down do not define a toolbar button.

Could you explain this part in more detail:

Some of my other settings are also botched up: tab used to open on hitting "return" among them.

You are hitting return on a link, bookmark, address bar text, or something else. And it opens in the same tab instead of a new tab?

Thanks for the response. Unfortunately it's incomplete

Both these issue occur on my Mac with Sonoma 14.3.1 which is the latest version

The first issue is inability to pin add-ons to the toolbar. It doesn't matter if the add-on uses only shortcut keys. I use the overflow menu for an app that doesn't require button activation. I still should always have the option to ensure that it's functioning correctly. And any developer should anticipate this.

As for the non-opening tabs issue: for at past 9 months, I have been able to open a new tab by depressing the return (or enter) key. Suddenly this feature is gone, only to be replaced by a "+" on the far-right hand top of the FF window. I have no idea why that happened. I tried in vain to find guidance on Moz Support pages: nada.

I also attempted to find a substitute add-on that would enable me have this feature again. There are none, save add-ons like bells-and-whistle stuff like Tabliss (why 80K people love it eludes me). I did find one app that might work, but of course the app didn't even load. Right now, I have to click this infernal "+" sign to open a new tab. I don't work this way.

Which leads me to yet another issue: the inability to open a new tab from a link in my current tab. While several add-ons purport to do this (and I tried both), they are buggy so as to make it impossible to use without causing freezes, crashes, and of course not doing what they say they do.

If you can solve these two issues, please do so. If you can't I completely understand. FF add-ons are a poor relation to Chrome--and for reasons like this.

The first issue is inability to pin add-ons to the toolbar. It doesn't matter if the add-on uses only shortcut keys. I use the overflow menu for an app that doesn't require button activation. I still should always have the option to ensure that it's functioning correctly. And any developer should anticipate this.

You can usually find contact information for an add-on developer using a link on the lower left of the listing page on the Add-ons site.

As for the non-opening tabs issue: for at past 9 months, I have been able to open a new tab by depressing the return (or enter) key. Suddenly this feature is gone, only to be replaced by a "+" on the far-right hand top of the FF window. I have no idea why that happened. I tried in vain to find guidance on Moz Support pages: nada.

My Firefox doesn't open a new tab every time I press the Enter key (the Windows equivalent of the Return key on Mac). I use the Enter key for so many things, like writing this post, that it wouldn't make sense for the Enter key to always open a new tab. Can you recall any details about when Return opened a new tab and when it didn't?

Also, do you recall your Firefox performing a Refresh/Reset/Tune-up? The tell-tale sign is a folder appearing on your Mac desktop named Old Firefox Data. If you see that folder, it may have clues as to your previous settings and add-ons.

Which leads me to yet another issue: the inability to open a new tab from a link in my current tab. While several add-ons purport to do this (and I tried both), they are buggy so as to make it impossible to use without causing freezes, crashes, and of course not doing what they say they do.

You usually can direct a link to open in a new tab by holding down the Command key while clicking the link. Some page scripts may prevent that from working.

Thank you for your responsw. An Old Firefox Data icon appeared on my desktop a week ago, but to be honest, I just deleted it. Re the return key issue, since it's gone now, I can't say that I ever had it. It was something that I have on Chrome. I'll just make due with the + sign for now. The feature I miss the most, which operates perfectly as a Chrome extension click opens new tab with link. there are two on FF and I tried them. Both caused issues that impacted my Mac. I can't describe the behavior because I've forgotten what arose. I did spend a few hours with an Applecare Sr. Advisor before we figured out the problem was in these addons.

In sum, my Firefox experience has not been great. Sorry.