I have been doing therapy via Skype since March instead of in person, and after ten months of opening Skype and calling my therapist manually, I wondered if Skype supported URL schemes. After a quick seach, it turnes out it does. I found them documented here.
In Fantastical (my calendar app of choice), I pasted the following in the URL field:
echo123 with the username of my therapist. It looks like it works on macOS and iOS.
Now, when it’s time for therapy to start, I can just click that link.