Hi,
You can create a entity with most of the common attributes used within those three entities and keep that as parent one
Then create three sub entities with remaining attributes from parent and make those entities as Generalized one
If you create an object for sub entity then it will automatically create an parent object with entities
Entity(Parent)
Mendix projects (Sub)
Power BI projects(Sub)
General Projects(Sub)
Exactly what Menagapriya wrote. Generalizations are documented in https://docs.mendix.com/apidocs-mxsdk/mxsdk/domain-model-metamodel#3-generalization-relationships