Is it possible to get an established Japanese Maple grow new branches? Over time the tree has had many of it's branches knocked off and it could use some new growth. I've read that maybe notching the trunk would stimulate it to start a new branch, but want to see what the experts think.

I've never heard of such a thing but maybe @OttoBjornson can help.

Posting photos would be helpful.

Yeah, I figured it was a long shot. I'll get a photo uploaded soon.

Japanese maple trees are very slow growers to begin with and generally once they have reached their mature size you would see very little in terms of new growth.
With that said, I should mention if a tree was under severe stress, for example if a main limb suddenly broke off in severe weather, then you would see new shoots appearing on the main branches where the break occurred.

Thank you Otto