More fields from Project Online should be added.The project ID returns a GUID but not the ID that on the Project Online site (column). Please add that.
If you know the name of the field in Project Online, you can use it in the expression field after the Fx sign:
for example: triggerBody()?['ProjectIdentifier']
I agree guys, we need to be able to pull the project id that Project Online is giving us. Using the GUID is a not a clean or easy solution.