Currently is possible to create onboarding group tasks to start after the hiring date but not prior to.

Certain tasks are done before the hiring date, such as creating user, giving access to systems, setting up the workplace, etc.

I know it sounds trick and it's a chicken egg situation.

Maybe adding the ability of creating a reminder like 5 days before the due date would help.

Scenario:

Task Groups created > Tasks created > Create Automation > Set "0" as "days after the hire date" > Set reminder as "x days" before the start date.