Operating system: Darwin-18.6.0-x86_64-i386-64bit 64 Bits
Graphics card: AMD Radeon Pro 570 OpenGL Engine ATI Technologies Inc. 4.1 ATI-2.9.26
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-06-04 13:15, hash: rB5361fc2c3325
Short description of error
Using OSX and Italian keyboard some function are not available and is impossible to remap some keys since blender seems to reject their input in the keymap inputs.
Exact steps for others to reproduce the error
open blender on osx with Italian keyboard and try to activate the viewport pie menu. since the key "\" is Italian equivalent to tilde try to map that key in the keymap editor to replace the tilde. Blender will reject the input and ask again for a keystroke.
attached a sample of Italian keyboard. Other keys are not mappable. Search for brackets [ ] equivalent and so on.