I just pushed a new version where it'll use a thumbnail if Windows already cached it. We tried a few different things and they were all not satisfactory, mainly because it just super expensive to traverse folders and cache thumbnails in UWP. So that's the best we can do 
Basically if you wan to have a dedicated thumbnail for all your folders, put a picture in the folder and name it folder.jpg (or any image extension) and have Windows Explorer view the folder in large icon (or bigger), then the thumbnail will be cached, and it will be available to Comics++.
You'll be able to try it out in a few days.
Basically if you wan to have a dedicated thumbnail for all your folders, put a picture in the folder and name it folder.jpg (or any image extension) and have Windows Explorer view the folder in large icon (or bigger), then the thumbnail will be cached, and it will be available to Comics++.
You'll be able to try it out in a few days.