Easy to create a second profile based on an existing one. Start "Mach3 Loader" (which is an application installed as part of the initial Mach3 installation). That gives you the opportunity to create a new profile (just click "Create Profile"), and then tell it which profile you want to use as a starting point. When you load it for the first time, it creates the relevant folder in the macros folder and copies over the macros from the starting profile you specified. You'll probably want to create a new icon on your desktop - copy an existing Mach3 shortcut icon (such as mach3mill), right-click on it, select properties, and in the "target" entry, replace mach3mill with whatever your new profile name is. If your new profile name has spaces in it, then put the profile name in double-quotes (e.g. "router mk2" in my case).

Job done!

You can have as many different profiles as you like, as far as I know. However, there does seem to be a gotcha. If you are using a CSMIO, you can only have one set of CSMIO parameters per machine. That is, all the profiles that use the CSMIO also use the same parameters for it, the ones you set in the config plugins->CSMIO page. That might not be a limitation if you want different profiles because you are playing with different screensets and/or macros for each profile, but it's all with the same machine.