Hi, for Customize Firefox, that is part of the 3-bar menu, so you can't remove it, but the tab can be closed in the usual way by clicking on the 'x' Close Tab.

For the Options tab, you can close it as above, or you can go back to the old Options window by: Type about:config into the address bar, press Enter, accept the warning, scroll down to browser.preferences.inContent and double click to change 'Value' from True to False, taking care not to alter anything else. You may then need to restart Firefox.

If your question is resolved by this or another answer, please take a minute to let us know. Thank you.

There is a long-term trend in Firefox to stop using pop-up dialogs and to replace them with interactive pages that display in a new tab.

You can open these interactive pages in a separate new window using one of these techniques:

• (after the page opens in a tab) right-click the tab > Move to New Window
• launch the page by bookmarking it and Shift+clicking the bookmark instead of using the menu

I'm not sure what add-ons you've tried, but perhaps one might have a specific option for pages like these that switched from a pop-up to a tab.