Project Timecard Approvals route based on Project Type

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Hello,

We have a requirement to separate Internal time (holiday, training etc) approvals and Project time. The requirement is as so;

-Send project/ billable time to be approved by the Project Management. Is the Project Manager cannot be identified for the project, reroute to the PM's Line Manager.
-For Internal time (holiday, training), auto-approve the time.

I have been informed that it is possible to do this by project type, to allow the 2 types of approval. However, they could not inform me how. I have tried to figure this out/ find it documented, but I cannot find anything. please can someone help??