Slack uses command-K for all Open Item commands, whether they are DMs or not. It also uses the full title as the typed search for command-K.
DMs links are created in Hookmark as “ (DM)” which is the right window title, but then, running command-K “ (DM)” will actually search for all occurence of “” and “DM” in Slack.
When opening a DM, Hookmark should directly send command-shift-K and the “”, maybe?
I haven’t tested with multiple users DM channels though, I suspect there could be interesting issues in here too 