FTM-400, Digirig mobile and PC as mixing board

[Constrainted]

Ham-audio-bridge is a project to do what you are describing:

Use DigiRig v1.9 for USB microphone interface to radio mic audio input

@ve7tzb I think this project, ham-audio-bridge on GitHub, has the goals you set out in your original post. I have not tried out this software. Please post any feedback here because the author posts on this forum too. 73 Constrainted

Good luck.

73 Constrainted