Hi, I don't think Firefox has a feature to automatically load bookmarked pages into tabs, but Firefox does have some tab-related settings:

(1) A setting to restore the tabs that you had left open the last time you Quit Firefox. This is the first checkbox on the Settings/Preferences page.

(2) A feature to restore Pinned Tabs even if you don't set Firefox to restore regular tabs. (Pinned Tabs - keep favorite websites open and just a click away)

One other thought: if the problem is that Firefox always shows the Bookmarks Sidebar (Command+B), usually if you close the sidebar in all the open windows, Firefox will stop doing that.

Bookmarks still there. Thanks for trying.

Bookmarks still there. Thanks for trying.

Where are they showing up that you don't want them? Can you share a screenshot?