Test map attached to make it clear for you
Check in the Object Editor and such for Channel-based ability usage
You must remember, Channel is just a dummy, fake spell that is used to avoid the overlapping abilities only
The spell itself, doesn't have any unique benefits like heal a unit, or even damages enemies
It's mainly used for Trigger-based ability
Check out the Trigger Editor too in my test map, I had to use dummy unit to cast a spell, casted from a dummy ability, Channel
In the test map, at your left, there is a Blood Mage with 2 abilities of the same Base Order ID, when you cast one of them, both spells will appear to have been activated at the same time
Whereas at your right, the Blood Mage has 2 abilities that have same function, but different Base Order ID, therefore, there will be no overlapping of abilities issue for that unit
Notice that the Channel ability, I changed its "Data - Base Order ID" from "channel" to "charm"
You can change to whatever you want except retaining its current Base Order ID which is "channel" or other Base Order ID that have the same Order String with any other abilities to a (1) unit