I’m reading Pinching vs. Pruning | Bonsai Mirai where it talks about pruning only when the tree is an energy positive state. How do you actually tell this? Do you look at the roots? The foliage? The speed of new growth?
It comes down to foliar mass.
For deciduous and elongating species, you want the foliar mass to be more than it was the previous growing season. This tells you that the tree has extra resources to be able to produce that extra foliar mass. Also, remember that trees have energy reserves, so during a repot one can tell if the tree is in an energy positive state if the tree produces foliar mass and then continues to had additional mass through the growing season. Deciduous have a faster allocation of energy and they can move resources quickly. You can work more frequently on deciduous than you can on evergreen species.
You can tell if an evergreen species, such as pines, are in a positive energy state if they add additional foliar during the growing season. You have to be more patience with pines because they move resources slower and it can take some time before you see an increase in foliar mass. You tend to see practitioners wait a few years between any major events such as repotting or restyling.
Good comments by @pj86. I would add that a tree is not in an energy positive state when it has been repotted or pushed a bunch of new growth that has not matured/hardened off. It has used it reserves to grow new roots or foliage and needs to use them to regain energy.