Update an external training while pending approval

Summary

Is it possible for the user, or an admin, to update an external training request when it's pending approval by the supervisor?

Content

Hello,

We'd like our users to be able to update their external training request when it's pending the approval of their manager.

The rationale is that they often have more details to add after the initial demand, or they'd want to change the date for example. Since the manager has not approved yet there is no harm in changing the request.

Can this be done by the user? Or, at least, by an admin? We can't seem to be able to find how,