even easier!
put all your configs into the config folder
then just set which on to use

 #!/bin/bash
 # set my config 
 export MM_CONFIG_FILE=~/MagicMirror/config/config1.js
 # then call mm.sh
 exec ~/MagicMirror/installers/mm.sh

thanks @strawberry-3-141

Enable ability to set configuration file by the environment variable called MM_CONFIG_FILE.

To test it you can run MM_CONFIG_FILE=YOUR_PATH_TO_CONFIG_FILE npm start in the terminal.

MM starts with a script installers/mm.sh (or u can create your own)

anyhow…

lets create run1.sh in installers

#!/bin/bash
# copy my config.js into the folder with the required name
cp ~/MagicMirror/myConfigs/config1.js ~/MagicMirror/config/config.js
# then call mm.sh
exec ~/MagicMirror/installers/mm.sh

then after saving, do

chmod +x run1.sh

then whenever u want to run MM with config1

just do

~/MagicMirror/installers/run1.sh

u can shorten the commands if u are in the MagicMirror folder at the time…

create as many run?.sh as u need

I might save the original config.js in your folder too