Q.rubber tree
I’ve just snapped a large branch off my rubber tree. It’s still rooted and there is new growth on the branch. Can I do anything to anything to save it?

The best thing to do, as long as there is new growth on the branch, is pretty much leave it be. The branch on the mother plant should heal itself and continue sprouting new growth, or you can perform some light pruning to help it regrow. You can use the branch that you snapped off to start a new tree. These articles may help you:
https://www.gardeningknowhow.com/houseplants/rubber-tree/prune-rubber-tree.htm
https://www.gardeningknowhow.com/houseplants/rubber-tree/how-to-care-for-a-rubber-tree-plant.htm
and
https://www.gardeningknowhow.com/houseplants/rubber-tree/propagation-rubber-tree-plant.htm