Opening in a new tab is only available for a bookmark like you see from the name of the browser.tabs.loadBookmarksInTabs pref. For history items you need to middle-click or any other way that forces a new tab (right-click context menu or Ctrl + left-click).

There is no setting for opening Browsing History in Tab automatically with just a left-click. browser.tabs.loadBookmarksInTabs works for Bookmarks, but not for Browsing History even though both appear in the Library.

It's a pity that it isn't possible and I hope the developers will add a setting for this. To be consistent with opening links and urls in a new tab it should be possible to change the default behavior for history links too.

I have sort of the same issue. I had FireFox set to open links in a new tab when I clicked on them. All of a sudden it stopped working. Did they change something? How can I get it back?

The setting in "Options/Preferences -> General -> Browsing" to open links in a new tab only applies to links that specify a target window. The setting specifies whether to open the link in a new window or in a new tab. You can middle-click a link to force the link to open in a new tab. Only with bookmarks and with search results you can force to open a new tab via prefs on the about:config page.

It's been a few years since I noticed that Firefox behaves this way. This is infuriating! I usually open History using Ctrl+Shift+H (Windows) and then History opens in a sesparate window so I cannot see what is below. Then I double click something to open it... and it uses the open tab to load the link I clicked. Totally counter-intuitive!

It is frustrating but you can get around it by right clicking on the link and select open in new tab.

If you have a mouse with a clickable mouse wheel then you can middle-click the link to force it to open in a new tab. You can also use the history sidebar (Ctrl+H).

It's been a few years since I noticed that Firefox behaves this way. This is infuriating! I usually open History using Ctrl+Shift+H (Windows) and then History opens in a separate window so I cannot see what is below. Then I double click something to open it... and it uses the open tab to load the link I clicked. Totally counter-intuitive!

IMO, that separate window will be changed in the future. Mozilla is slowly rebuilding Firefox and has already eliminated some "separate windows" as part of the "stages rebuild process" that has going on for a few years already.