If someone of you used the Opera browser, you probably know that this browser uses the preview tab or the preview in the pop-up window when the mouse cursor even on a closed tab. Now this function can be installed in Firefox, as an addition - Tab Scope.
Sorry for the spelling and phonetic errors in the text.
Owner and main writer of MintGuide.org is not a native English speaker.
The addon of Tab Scope has its own settings where you can change the size of the popup window, design, layout, animation, and much more:
Use this link: Tab Scope.