XYplorer Beta Club

For the same reason (efficiency/speed/repeat use) as caching search results and thumbnails?

I'm thinking here especially of the very slow processes like calculated columns, and columns containing hashes. There's a caching mechanism for per-file data already (thumbnails); can this be extended to create options for caching custom column data?

Useful if you want to repeat a search or refresh a folder, and not have to recalculate them all again.

Good idea but e.g. for your example of stored hashes:
To make sure you see the real data (and not some cache results)
you would have to refresh the column anyway (if it's not only a single item)

Scripting can help a bit atm:
viewtopic.php?f=3&t=16565