Can I make "My Categories" into keywords efficiently?

[DONUSA]

I've used My Categories to put many thousands of photos in hundreds of categories using a hierarchy I created.  I'm regretting this now and wish I had just used keywords so they are part of the metadata written to the file.  This would be very helpful for when I am in another app, like Lightroom, and just want to search for a photo(s) by keywords. 

I can open each of My Categories and then create a keyword for all the files in that category, but that is going to be a lot of time and effort.  Is there any way to just make the category the file is in into a keyword for those files?  Even better if it can be a hierarchy keyword. 

[Mario]

IMatch categories have many advantages over simple keywords. And they allowed users to manage their files in a hierarchical organization long before hierarchical keywords even existed.
Not to speak of powerful IMatch category features like formulas or data-driven categories for automatic organization of your files.

The special @Keywords category automatically organizes your files by the keywords they contain. If you make changes to @Keywords, these changes are also reflected in the keywords of your files. @Keywords was introduced in IMatch 5.

If you manage your files in a totally separate category hierarchy and you want to convert the category assignments to keywords, the best way would be a metadata template. Use the hierarchical keywords tag as the target, and a variable representing the categories you want to copy into the keywords as the source.
This workflow has been discussed many times here in the community, I think the last time just one or two weeks ago.

This very question is answered (in form of an example) in the Metadata Templates help topic in the IMatch Help System: Copying IMatch Categories into Keywords

A quick search in the community for the words categories keywords immediately revealed this post https://www.photools.com/community/index.php?topic=10999.msg78380#msg78380 as the second result. This should answer your question.