I figured it out. This functionality was actually from the 'Cursor Enhancements' mod by author Raiguard. From the changelog of that mod:
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Version: 1.1.0
Date: 2020-11-23
Features:
- Added item name labels when scrolling between items
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At some point it appears that this functionality was removed from the Cursor Enhancements mod, though it is not listed in the changelog.
For what it's worth, I still believe that this would be a good feature to add to the awesome OSHA Hot Swap mod.