Log unilateral reps and/or double weights

This seems to be an issue and a request for many workout apps, but I wanted to request it from my favorite workout app GymBook as well.

The issue is about getting the correct number of reps when lifting a weight first with one arm and then with the other, for example.
The same issue applies when using double weights, like doing dumbbell bench press for example.

In the app I want to see which weight I should use on each dumbbell. Or how many reps I should do, per arm.
Then I want the app to correct the summary to show the double amount of reps, or weight, or time. Depending on what kind of exercise we’re talking about.

I know there are workarounds where I could just add one set / arm instead, or double the amount of reps or weights when logging, but that’s not a very elegant solution.

Could this functionality be implemented?
I think it would make several users choose GymBook instead of other apps.