Win10: Change default app by protocol


I have once the following question:
Is it possible to change a default app byt protocol (here: TEL URL:tel) to a program?

I would like to have the following. I want to dial a phone number directly from my merchandise management program (WaWi). For this I have installed as softphone Jitsi. The general dialing procedure via Jitsi works, i.e. my Outlook contacts are displayed and I can dial them. But if I want to dial via WaWi, I can’t select Jitsi - ther is no app. I can select “With your smartphone”, but I can not select a wired phone, because this requires an app on the smartphone. Is there any way to assign this protocol to Jitsi, or is there another way how I can get this linking working?

Thanks, Dietmar