I posted that originally on Discord server, so I am reposting that here, so it won't be forgotten.
I haven't seen this request but, I think it would be nice to have visable keys in your HUD. Build Engine ports have key indicators in your HUD. In DF you can only know which keys picked up by going to the PDA
Could look more or less like down below and of course it should be toggleable in options.
That definitely looks useful and fit in nicely with other HUD features like scaling and offseting. Though it will require either expanding the left "offscreen image" or adding a new one. So probably something to be added near or after the 1.0 release.