1 Rep Max and Percentages Per Exercise

I've been doing some blood flow restriction training... most studies are done with 20% of a 1 RM for a given exercise.  However, it would be great to see my barbell curls and have DR Muscle estimate my 1 RM... and then show me the percentage breakdown. 

There's plenty of web calculators that do this already I know but moving from exercise to exercise, I am not sure what my 1 RM for should press would be without going outside of the app and then guessing.  But Dr Muscle probably already knows my best and highest weight I've used for dumbbell shoulder presses since I started using it and would have a better idea of my true 1 RM and what 20% of that 1 RM realistically be.