I'm not excited by this addon, but it does the job well enough for my needs. It's easy to set up, easy to update the thumbnails, and also easy to manage the websites because they are all stored in a single bookmark folder. Also it doesn't ask for too many permissions.

What can be improved? It does not generate the most attractive thumbnails possible; the screenshots are not zoomed in enough. (For an example of what I'd like, see how the Vivaldi browser does thumbnails.) I have tried various options to zoom in manually, but the result has only been good in one case.