"Cancelling a scan" feature is forthcoming. Regarding the process priority request, what do you expect to gain from such (honest question)?
Sometimes the window gets unresponsive while handling a lot of files. That's why I suggested priority similarly to how archive managers handle things. I'm not sure if it's possible.
Also, it would be very interesting to see a cache system that might speed up the process since some files might have been (already) processed.
Perhaps there should be another action in "View" tab that gives end-users the ability to show only unique files (not duplicates).
Another issue that I've observed is that it does not handle special characters well. Probably a display issue.
And another suggestion would be to rename "Trusted list" to "Trusted Vendors" as this might avoid possible confusion & make the box re-sizable.
I've seen that you get to choose from three different search providers. However, why not let the user choose additional ones? Perhaps it should be configurable since some users might have access to executable databases by using hashes (or other information). Thus, another useful suggestion would be to allow macros. As for example, the user could input $
SHA1 (and other) in the url.
Example of such usage (but not necessarily limited to VirusTotal) : https://www.virustotal.com/en/file/$SHA256
While I do like that you can use "Open VirusTotal URL(s)" from the right-click menu, it is unclear on how to actually use it from a novice user point of view. This action is available/enabled by default. I'm not sure if it is intended since you can spam this action while not doing anything and not being ok from aesthetics point of view.
Also, the clean action will not do anything if files are being processed. I'm guessing this option could be grayed out or/and inform the user that it is not possible, maybe.
Under "Help" tab > "Contents", users would expect a help file and not a pop-up that describes SigcheckGUI since there is an "About" button. Superseded.
Another suggestion that might be useful regarding quick access would be to add another action in the right-click menu named, for example, "Open File Location".
Maybe, the "Info Box" action from right-click menu should be grayed out for multiple files.
heckGUI or SigC
heckGUI -- Is it intended?