I don’t know what the use case is, but it seems to me, as far as with using the web UI, it would be easy enough to reset the bump date of individual topics when they were bumped. I’m not seeing how “bulk bump date reset” would ever be needed let alone a common enough need for it to need to have a UI.
Anyway, if you’ve somehow managed to get in a situation where you want to work in bulk, it should be possible to do using the CLI