In addition to Bram's answer: In version 2.X of the Mendix Business Modeler, an explanation of setting up a multi-development environment is given below:
In order to view what parts of the model other developers are working on, you can use the "Documents Being Edited..." functionality.
Some remarks on multi user development
The short answer is, that it allows you to have multiple people working inside your project at the same time.
By locking microflows and forms the modeler prevents you from both trying to edit the same form/flow at the same time.
Thanks all. I conclude that the best way to start a MDP is:
make a new database and db user
in the modeler, create a nwe MDP
immediately go to Project Settings/Disk locations and define the project directory (and let the modeler create the necessary subfolders). That prevents prompts for the project directory when pressing F4 or F5.
set up your version control