I abandoned Maximus ages ago. But how do you get Steam games to work with their proprietary URL shortcuts?
Just point to the game EXE instead.
That doesn't work with some Steam Games.
Ok, I figured this out for ya.
Step 1 - Right click on game in Steam and "create shortcut on desktop"
It should look something like "steam://rungameid/282440"
Step 2 - Create a batch file (plain text) called something like "game.bat"
Step 3 - In the batch file put "explorer.exe steam://rungameid/282440"
Step 4 - Point front end at the batch file you created.
If Steam isn't running, but is registered properly, it'll start Steam then start your game.
(steam://rungameid/282440 is Quake Live on my system - don't know if that's universal or not)
Enjoy!