There should be no limit.
Can you zip up all the Catalog files and send them to us for testing? If they are to large to email, send via www.wetransfer.com
support@ironcad.com
Check this Microsoft article:
https://answers.microsoft.com/en-us/windows/forum/all/file-explorer-freezing-randomly-in-wnidows-11/4e91960f-d50b-49e3-a890-e5842223dde5
The Custom Property template should store here:
C:\Users\%USERNAME%\AppData\Local\IronCAD\IRONCAD\26.0\en-us\PropertyTemplates\NewTemplates
You will need Full Control permission in that location.