That would be complicated. Shortcuts always execute immediately and macOS doesn't have any support for multi letter shortcuts.
It can be done but it's quite advanced and complicated, also in that case you'd indeed need to use key sequences. It would require usage of the "start blocking keyboard input" action once right cmd is pressed and "end blocking keyboard input" once right-cmd is released.
This can then be combined with a conditional activation group that is only active while keyboard input is being blocked. Additionally the "d" key sequence would need to be configured to only trigger if no other keypress is detected for a while.
