I understand the move past Snow Leopard meant losing Rosetta, and compatibility with any PPC apps.
Since there are some apps that can't be replaced (for example, old years of TurboTax that I might need to reference) I have a drive to boot Snow Leopard, and one for Yosemite. I was considering the jump to El Capitan, when I saw the question Is VMware Fusion 5.0.5 compatible with OS X El Capitan? which got me wondering the question -
Before installing a next generation OS, is there any way to find, in advance, which apps I have that would be orphaned by the move?
Edit, the answer below from Jean Valjean was what I needed. One app concerning me appeared as follows:
It might be tedious to search many apps, but at least this gives me a chance to view the top ones that will cause me grief.