Firebase + Tag Manager: Fetch variable from previously sent event

With the previous version of Tag Manager (dataLayer), it was easy to fetch variables sent within previous events, when those variables weren't sent with the current.

How to persist parameters with the Firebase version of GTM?

For example, previously, I could send an event with a user_id variable at the start of the session or as soon as the user logs in. I would then create a "Data Layer Variable" in GTM and use it to get this user_id at any subsequent point in the session. For instance, to send it as a GA custom dimension on a purchase event possibly made later.

Now, if I push a Firebase event with a custom parameter user_id and then create an "Event Parameter" variable in GTM, it will only be available within this event.

Same if I send a user property with Firebase and register a "Firebase User Property" variable in GTM. I won't be able to use this variable within an event at a later point in the session

Is there a way to persist user properties and event parameters?