Physical Bluetooth Keyboard is not able to access to chats (Whatsapp, Telegram) in Android 10
I don't think that is possible with a physical keyboard yet. I tried every key and many combinations too.. failed..
Then i tried remapping the key(one and only relevant function available is select/enter which does not work for selecting chats).. failed again..
I downloaded a physical keyboard helper(nothing helpful in it).. it failed too..
I think you'll have to tap the chats on the phone everytime you want to open any from the app.. OR you can create chat shortcuts on homescreen but that will be too weary adding every contact and messing up your homescreen.
An efficient solution will be to use a cursor (controlled from keyboard)