The feature where you can quickly change a brush size/ diameter by pressing Alt + hold right click (for Windows) (In Mac, control + alt + left click) is neat but is there any way to change that shortcut to a different combination? I can't find it in the shortcuts list.
Not aware of a way unless it could be done via scripting or a program like auto hotkey.
There are the legacy keyboard shortcuts for brush size and hardness (left and right bracket keys for size and add shift for hardness)
and those shortcuts can be changed under keyboard shortcuts>tools.