Work simultaneously on different projects and copy-paste each interesting parts of them in one common project.
For now it's not possible to work together simultaneously on the same project because if someone changes something on his screen, changes he made will impact screens of the other workers.
That's why we recommend you to not work together simultaneously on the same project.
If you want to work in team on a project, juste create different project (each project is a work place to create a animation, a screen, an action...) and copy-paste your creations on a common project.
This functionality is available with Pro account.