Back in July of 2013, someone asked the question of how he could have IMatch show a list of the categories to which a file is assigned in the thumbnail panel. The link to this topic:
https://www.photools.com/community/index.php?topic=433.msg2353#msg2353
I tried that, applying it to the "Thumbs Only" thumbnail preset. The result is that IMatch would basically hang. I couldn't really scroll in the file window, and things would just generally freeze up! What can I do to troubleshoot this?
This behavior may be caused by an excessive number of categories to display for each of your images.
The file window has to load the categories for each file in the file window, format them according to your category formula etc. in order to know the required height of the panel and what information to display. This can be a slow process if your files have many categories. There are technical and performance limits not even IMatch can overcome.
Please
a) Show us the variable expression you have used.
b) enter the same variable expression App panel and show us the result for some of your files.
c) Enable Debug logging under Help > Support and attach a log file from a session where you tried this out.
How to report bugs (https://www.photools.com/community/index.php?topic=22.0)
What can work if your files have a couple of categories will cause performance issues if your files have dozens of categories.