Rated 4 out of 5 stars

4 stars because it really needs possibility to save/load disabled list sites

This review is for a previous version of the add-on (3.3.1-signed). 

You can enter sites you want to disable into the Thumbnail Zoom Plus preferences "Disabled Sites" dialog. Those will be saved (remembered) for future sessions.

If you want to save the text of the setting, e.g. to copy to a different browser, it's not officially supported, but there is a way:

Enter about:config into the Location field. If prompted, tell Firefox to continue. Then enter disabledsitesRE into the Search field. Double-click the item to copy or paste its value.