First things first: there are two different smartthings app’s. The legacy one, called “classic“ is still used by many customers. But the current app, which we call the V3 new app in this forum, is the one that you should probably start with since you are a new user. But let’s just make sure that you did get the correct app:
(The topic title is a clickable link)
The second thing is that the new V3 app has been changing very rapidly and in quite significant ways and not all of the documentation has kept up with it. For example, what were called “custom automations“ just a couple of months ago are now just called “automations.“
This has been a continually frustrating fact of life with smartthings: rapid rates of change can be good or bad, but undocumented rapid rates of change can be very hard to keep up with.