In Myriad v3 the process for adding multiple configurations has changed somewhat as there is no longer an independent Myriad Configuration program and the settings are now stored in the Windows Registry rather than ini files.You will need to enable multiple profiles in the main Myriad program by looking in the Menus for Settings > Myriad Settings, then selecting the Advanced tab. You should now be able to click the Manage button for Configuration Profiles.
To add an additional profile, click on the green + icon you will be asked to enter the Profile Name. To keep things simple it is probably best to call this Profile2 to match the default Profile1 that already exists. You will then have to enter a description for the profile, which can be anything.
Once you have more than one profile, you should be asked on restarting Myriad which one you would like to use. Choose the new profile, and you will have to enter all the details of file locations and soundcard setting as if the Myriad install were new. Unfortunately, there is no option to copy the existing profile, so any settings you have modified in the original will need to be manually duplicated in any new one.
As with Myriad v2.6, if you create 2 or more profiles, you may wish to avoid being asked which one you would like to use on starting Myriad. This can be done by adding a command line switch to the Myriad shortcut. Add to the end on the shortcut target " /profile=profilename" (not including the quotes) to load the desired profile automatically, where profilename is one of the names you gave to the profiles you created.