Select app in Positron to use with "open with" for specified file types

Hello all,
I'd like to be able to open certain file types with programs other than the default editor in Positron. For example, I'd like to open .pdf files with Mac Preview.app. I'd also like to be able to open .tex files with MacVim.app. When I click on "open with" and then "configure default editor for ..", and then enter the path/filename to the app, Positron does not open with that app.
Can anyone tell me how I could set up other apps to open specific file types in Positron?
Many thanks,
Joe Retzer