I guess I'm not understanding, though...
If you have this line stored as a macro:
!cmaster --add,condition=concentration,duration=?{Duration|1},direction=?{Direction|0} {&select @{target|token_id}}
... and you send that macro to the chat, you should get the prompt for targeting.
Roll20 will turn your click into the return value for removing the @{target} structure, and your line will effectively look like this:
!cmaster --add,condition=concentration,duration=?{Duration|1},direction=?{Direction|0} {&select -MaVv0IALIj6_SZ-sbtM}
Then SelectManager uses that {&select} structure to add the token matching THAT ID to the selected tokens for the message.
Then CombatMaster gets the message with that token apparently "selected."
The only way this doesn't work is if you call this command line from a script... in that case, there is no "source player" who can see and respond to the targeting request, so nothing gets populated to that part of the line.
If that's not what you have going on, then help us understand how you are currently storing and calling this command line, what the resulting behavior is, and how that differs from the behavior you expect or want to see.