Thanks for these suggestions, Colin. We have tried to make these operations keyboard accessible: Shift+P adds a new player and shows the popover so you can choose an instrument; Shift+I shows the popover to add a new instrument to the existing player; Alt+up/down arrow move the selected player(s) up and down in the order; and Delete will delete the selected player (and its instruments).
So I would suggest you try Shift+P followed by Shift+I to add players and instruments: I think you will find it a lot quicker.
One current problem is that you can’t hop the selection up and down the list with the arrow keys alone, so you can’t easily select the ‘Empty-handed Player’ to delete it without picking up the mouse, but on the other hand, you don’t actually need to delete said player, as it doesn’t add any staves or other data to the project until you eventually assign an instrument to it.