Q.buds set (Magnolia)
www.gardeningknowhow.com/ornamental/trees/magnolia/propagating-magnolia-trees.htm :
“…after the buds set.”
I would like to know what that means.
First, does it refer to flower buds? leaf buds? either?
Second, what is “set”? By what do I recognize “set”?

Certified GKH Gardening Expert
Magnolia send flower buds in late winter and early spring. The article states that this process will be done in summer, so this would imply that it would be the leaf sets that you will be looking for. In this case, set, refers to the action of pushing out buds. This is the term for bud growth, "bud set".
As long as you do this right after you start seeing new growth in the Summer, then you will do just fine. The reason for this, is that Flowering hormones inhibit Rooting hormones, and vice versa.
Just take as many as you can without taking all terminal ends from the tree. You will need as many as you can manage to get one good rooted cutting. These don't root very reliably.