Setting up a new softphone (Specifically the Comcast SoftPhone application) on some Windows 10 machines and the “Choose Default App” within Windows 10 was not letting me select a custom .EXE application to open with the tel: URL protocol. I found a work-around buried in the old Control Panel options.
Here is a quick, step by step guide to make changes to the tel: URL protocol in Windows 10.
Step 1: Open the “Set Default Programs” within the Control Panel
On your keyboard press the “Windows Key” and the “R” key at the same time.
Copy and Paste, or type in the following command:
control /name Microsoft.DefaultPrograms /page pageDefaultProgram
Step 2: Select the app you want to open when tel: is clicked.
Select the app you’d like to open the tel: URL’s (in my case it is the Comcast Softphone app, but it could be any app for you).
Step 3: Select TEL and save!
Select the “TEL” (URL:tel) option and then click save.
That is it! You are done! Next time you click a tel: URL it should open with your previously selected app!