Workaround until this gets implemented:
Orion creates the proxy apps here:
~/Applications/Orion/Orion Profiles/
For each profile there is a folder with a UUID, and inside there is the proxy .app
. In Velja, when setting up the rules, open the "Open In" dropdown and select "Other". Browse to the proper proxy .app
and select it.
I have not used Choosy but I have also used Finicky in the past and I believe this can be achieved in a similar way with Finicky as well.