I am very new to dopus and I would like to ask a question. When viewing media files in Thumbnail mode, there is a small picture displaying the file extension of the thumbnail in the bottom-right corner (please see the picture in the link below). I was just wondering is there setting in Preferences to increase the size of such picture to make it bigger. Thank you for your help.
There isn't, at least currently and without changing system-wide settings.
It uses the file types' small icons for those overlays, and the size of those is a system-wide setting (normally tied to DPI).