Consider the following snippet of a simplification of an algebraic expression. The left-hand side has the usual notation and the right-hand side uses ditto marks to mean “the same as that part of the expression above.”
Notice how the ditto marks allow you to focus your attention on the pertinent part of the current step. This idea has possibilities. Next term I intend to try this method when I explain algebraic simplifications in class. I also intend to allow students to use ditto marks on their tests as a time-saver if nothing else.
When I coach students struggling to understand chemistry/physics problems or derivations, I always recommend that they look at what changes on each line and then try to understand why. If they replace what remains the same with ditto marks as I have done below. It might help.
I might have got a little carried away on the second line but it seems pretty clear.