You should contact Tab Mix Plus support on this.

Can someone explain how to use about:config to enable new tab openings from search bar and address bar? Thanks.

You have browser.tabs.loadBookmarksInTabs = true for opening a bookmark in a new tab. For the location bar you need to use Alt+Enter or middle-click the location bar Go button.

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

More info on about:config: Configuration Editor for Firefox. The moderators would like us to remind you that changes made through this back door aren't fully supported and aren't guaranteed to continue working in the future.

(2) In the search box in the page, type or paste intab and pause while the list is filtered

Q: When I type in search bar, open in new tab.

(3) Double-click the browser.search.openintab preference to switch the value from false to true

Q: When I type in address bar, open in new tab.

(4) Double-click the browser.urlbar.openintab preference to switch the value from false to true

Q: Currently, links still open in new tabs but not bookmarks and history.

This is for bookmarks; there isn't a similar preference for history:

(5) Double-click the browser.tabs.loadBookmarksInTabs preference to switch the value from false to true

Q: Have new tab open at far right (be the last tab) so it is easy to locate.

(6) In the search box in the page, type or paste insert and pause while the list is filtered

(7) If the browser.tabs.insertAfterCurrent preference has been modified to true, double-click it to restore the default value of false

(8) Double-click the browser.tabs.insertRelatedAfterCurrent preference to switch the value from true to false

Note: If the problem is where links open from pinned tabs, I think there is an add-on to change that.

Q: Ability to protect pinned tabs to protect them from being accidentally closed.

How you are accidentally closing them?

Note that you can't close a pinned tab via "Ctrl+W", this merely switches you to the first not pinned tab. You can always reopen a tab you closed via the "Ctrl+Shift+T" keyboard shortcut.

jscher2000, thanks so much for your help! Your directions were exact and easy to follow. A little history about me and Firefox. I began using Firefox eons ago and was an early supporter, back in the day when a lot of open source programs were being developed. At some point, however, I began having problems with FF that I couldn't resolve; it had become too complicated and I switched for, several years, to PaleMoon. With PaleMoon there were problems with websites opening or operating properly that kept getting worse, so I just switched back to Firefox. It was in PaleMoon that I had problems with my pinned and protected tabs just disappearing or suddenly opening in new windows. I have a mouse that does random stuff (also have Win7) and one or both of these likely resulted in some "command" that caused the strange behavior. At any rate, now, with your help, I'm happily back with Firefox and perhaps FF will not be as susceptible to the "mouse" attacks! Thanks again.