I have just recompiled a new version of FotoSketcher 3.30 for MacOS, which solves the trackbar bug (where the trackbar cursor positions would not update properly).
This makes FotoSketcher much more usable on Macs. I have successfully tested on MacOS El Capitan.
To download, head over to https://www.fosshub.com/FotoSketcher.html.
Some Mac users have mentioned that they were unable to download and install on MacOS El Capitan, due to security reasons.
This is because I do not have an Apple developper ID, not because FotoSketcher is a dangerous application (just make sure you ONLY download it from the official page https://www.fosshub.com/FotoSketcher.html).
Here is the Apple support answer to this problem: https://support.apple.com/en-us/HT202491
Have fun on your Macs!