SConsole is a fully customizable terminal for your GMS2 projects that already has loads of included commands and more on the way.
helpcommand which gives you all the info you need on every command.
varcommand which allows you to edit any variable values. This is VERY useful!
hitboxcommand which allows you to see the hitboxes of all instances, and show if they are colliding with anything.
movecommand which allows you to move any instances around your rooms.
destroycommand which allows you to destroy any instances
scriptcommand which allows you to execute scripts with as many arguments as you like (asset comes with 3 arguments coded in, but you can easily add more if you need them).
disablecommands allow you to activate and deactivate instances at a time.
clearcommand which clears the console of all text.
gamecommand which allows you to restart you game, end your game, and later on will allow for more in depth game settings.
roomcommand which allows you to move to the next, previous, or a specific room as well as restarting a room.
This extension is a foundation for you to build your own commands, you can easily create very diverse commands specifically for your own games, that being said if you want a command you can always tell me! There is a README object which has some other useful info in it too.
I will be focusing on improving and adding more commands!