No, it is not by default: what you CAN do, is set everything the game will have from start: objects, layouts, variables, event sheets, etc.
then everyone can work on it's own version of the game. and then join the game manually using copy-paste:
You can copy paste new objects too, you copy from one project, and paste the object in the other's layout, all variables in the object will be transferred too
All this since the only way to copy paste events from a project to another, is if both projects have all the same things with identical names and variables.
This way you need to have a "central project" and someone in charge of managing it. and you can, for example, program an entire event sheet in a copied project, and then copy paste all of it in the main project. but you'll have to manually add everything you changed, removes or added, like if you changed the bullet speed of an object, which is in the project properties and not in the event sheet.
You could however learn to set all values via events and leave the project properties out of it.
It's all about developing an efficient tidy method.
Not easy though. But I guess with patience and discipline, you could learn to do it quite efficiently.