If you want a project thumbnail to be unclickable, place this script tag into your Custom HTML:
Replace 123 with the PID of the project that you'd like to make unclickable. To find the PID, see this article.
If you want to target multiple thumbnails with the same modification, put the thumbnails inside a comma-separated list, inside the script tag:
$('#item_123 a, #item_124 a, #item_125 a')
If you want a project thumbnail to lead somewhere other than its project, add this script into your Custom HTML. Replace paste_url_here with the URL of your choice:
This will not hide your projects' contents or make them unreachable. Viewers can still see any images you've uploaded into your projects through your Following page, or by using the text nav or keyboard shortcuts to navigate.