Is it possible to create custom indexes in Agenda 4.4?

Question

It looks that the answer is affirmative in version 5.0.0 of Agenda, but I was wondering if there is such feature in version 4.4.0. The only reference to indexes that I have found is to disable the default index when you instantiate Agenda, as follows:

const myAgenda = new Agenda({
  ...
  disableAutoIndex: true,
  ...
})

But this only enable/disable the default index created by Agenda.

Currently working with MongoDB, but I think that database is irrelevant in this case.