The second way, next to speed dialing, to quickly call a number from the smart watch is definitely the call log. Here’s the app for Garmin Connect IQ devices. It works nicely with both touch screens and physical keys.
The app on the Garmin Connect IQ Store: https://apps.garmin.com/en-US/apps/4187fab3-36d2-4fe0-ab60-4858424c5cbf
An Android companion app is required: https://play.google.com/store/apps/details?id=eir.garmin.log