Here's an example. I have opened my Leave Request App and modifying the content of the Data Table with the user Alex Wilber.
On another computer I log into the portal and open Power Apps with a different user, Megan Bowen. As soon as Megan attempts to open the Leave Request Canvas App she is prompted with a message stating 'Canvas is locked for editing'. At this point Megan cannot edit the App until Alex has logged out.
It is important to note this does not stop users from running the published Leave Request App while Alex is editing the canvas.
So how do companies with large development teams work simultaneously together on projects? The answer is not to create one large application that does everything. This is a big mistake. My advise is to break the project down into smaller components and then create a application for these components.
Each component should all work and interact together forming to the end user one large application.
This method allows developers to work on component application simultaneously and debugging a problem becomes exponentially easier as it can be located in one of the smaller applications.