What determines if an expressions.tmdl file gets created?

Hello JackZeeU,

as of my knowledge the expressions.tmdl file only gets created if your .pbix contains calculation groups (from Tabular Editor) or other advanced model expressions. If your model doesn’t have those, the .pbip export won’t include an expressions.tmdl — that’s why you sometimes see it and sometimes not.

So in short:

• With calculation groups/advanced model expressions → expressions.tmdl is generated.
• Without them → no file, because there’s nothing to store there.

Maybe you can verify that with your concrete examples?

If you confirm feel free to mark my post as solution. 

Best regards!