External applications optional client path options

For some sessions, I need to pass a private key file via command line to the external application (... -k !K). If the session does not have a private key configured, the application starts with the -k option alone. That application fails to start because the expected key file is not present on the command line. Is there a way to configure the terminal client path depending on whether the session has a key or not?

Thanks.

You can use !`...` pattern with embedded !K to execute a local command that takes a key path and outputs what you need based on it. For your scenario, simple if command of cmd would do. Like this:
https://winscp.net/eng/docs/custom_command#command

Great. Works for me. Thanks a lot!