Creating new record in a DB by using content from other DBs

Hi there.

I’ve been working with Adalo for a few months and am having difficulty with a specific task.

I want a user to be able creating a document (new record in a database) which he can share, print, etc.
The uniqueness (and my difficulty) is that for this document he is creating (I assume I must use a form), the user must enter various fields as well as (!) select multiple items from his favorite lists (records from another list/DB).

The content of those records he had chosen, needs to be added to the new record.

I have created a workflow, which hopefully explains it a bit better.

Anyone has done this before already?

Help is really appreciated!