A Data Project’s name is configured in the large property shown at the top of the Data Project Designer, below the toolbar:

Provision of a name is mandatory, and the value provided may be a maximum of 100 characters. The Data Project’s name is the same as the filename under which it is saved within the RPI file system. As such, it must be unique amongst the Data Projects in the folder within which saved.
You can edit a Data Project’s name by clicking the property. Complete the edit by clicking off the property, or by hitting return.