How to automatic set protocol association to application on firefox

Hello Community

I have modified a policies.json file which has the following content.

“policies”: {
“handlers”: {
“schemes”: {
“tel”: {
“action”: “useHelperApp”,
“handlers”: [{
“name”: “3CXDesktopApp”,
“path”: “C:\Program Files\3CXDesktopApp\3CXDesktopApp.exe”

This allows Firefox to link the application 3CXDesktopApp.exe to the protocol tel

When I click on a phone number on a website that has the protocol tel:+12345678 number, I get the following message.

Allow this site to open the link? You’ll need to choose an application.
Always allow to open tel links

I click on Choose Application and my 3CXDesktopApp appears. I can then activate the checkbox “Always use this application to open tel links” and click on Open Link.

Only then is the application linked to Firefox.

I need to distribute these settings to over 200 devices. So I have to do this somehow automatically in a configuration.

How can I manage this link via policies.json, Powershell, Registry or in another way?