Useful: How to check for 32-bit apps on your Mac (since the next MacOS, Catalina, will remove support for them).
There’s a column in the Applications list in System Information which you can sort by 64-bit Yes/No.
https://www.theverge.com/2019/7/25/8930345/macos-catalina-app-compatibility-how-to-desktop
Less-useful: You can’t easily just go to the app or its location by clicking. You have to copy the path from the info panel at the bottom and paste it into Finder. Seriously, Apple?
Fortunately on this system there were only a handful of old Chrome extensions and a couple of utilities that I don’t use anymore. Everything else has already been updated to 64-bit.