I agree with the OP that the option to store distort equations is essential to make this excellent option workable. Either as presets or, maybe better, as user functions.
I have other issues with equations though. The OP suggests to store equations as macros. This does not allow access to the equation parameters and, worse, it does not produce the expected results on all images. I noticed images of different size are transformed differently.
So for now my only option is to cut and paste the equations for each application. Please Serif, help us out here; this thread has been going for months and I have not seen a reply from the company!
(my experience is with Affinity Photo 1.9.0)
Joost
