This idea has been developed and deployed to Canvas
When using the Teacher app on either iOS or Android, as I'm grading my instinct is to press the Return/Enter key on the virtual keyboard to submit the grade that I've just typed in for a particular submission. However instead pressing the key simply minimizes/dismisses the keyboard, which is frankly useless. This problem is particularly egregious on my iPad for 2 reasons:
In the menu for the iOS version, the "OK" button is sandwiched between "Excuse Student" and "Cancel", forcing me to work slower than I'd like since it's frustrating hitting the wrong button (which happens more often than I'd like to admit).
I like to use a Bluetooth keyboard with my iPad to speed up the process, and not being able to use its Enter key significantly reduces its time-saving benefits.
I believe that this is a bug with the apps that need to be fixed, and initially reported it as such. However the Support Engineer who responded informed me that this apparently needs to be suggested as a feature request instead. I'm still trying to figure out how having the keyboard minimize instead of submit a grade could possibly be considered a feature instead of a bug, but in the meantime I appeal to the Community for your support in bringing this matter to the developers' attention.