You can use MiiTel Phone Desktop to make a Click to Call with each application that supports callto://, tel://, and miitel:// with the following settings.
When you create a link with the format miitel:<Phone Number> or miitel://<Phone Number> in each application, the link would be converted to allow MiiTel to start automatically and make calls. For example, a link to call a phone number of 0344054621, create the link miitel:0344054621 or miitel://0344054621. You can also create a link in the format tel:<Phone Number>, tel://<Phone Number>, callto:<Phone Number>, or callto://<Phone Number>, but this may require additional configuration. If the outgoing call fails, please configure the following protocol handler.
Settings for outgoing calls using tel:// and callto:// protocol handlers
Scroll down and select Choose default applications per protocol.
On Choose default applications perprotocol, click the name of the application or [+] button that appears to the right of TEL (URL:tel), or CALLTO (URL:callto) protocol.
Select MiiTel.
For tel:// :
Start FaceTime and click FaceTime in the menu bar.
Click Preferences.
On Preferences, select MiiTel.app from Default for Calls.
For callto:// :
If you have another installed application that uses the callto:// protocol handler, you can either uninstall that particular application use the open-source software SwiftDefaultApps to change the settings. (Please note that we will not be responsible for any problems caused by the use of this software)
Examples of applications that set callto://, tel://, and miitel://: