Hi @nickas :
I assume you want to use an email address in multiple flows:
1\Create a SharePoint list and add an "EmailAddress" Column
2\Add an record(whose id=1 ) into the table and update this item's "EmailAddress" field.
3\Get the item by id '1' in flow and then you could get the Email Address from this item's "EmailAddress" field.
4\If you want to change the email address in flow, just update the "EmailAddress" field of this record whose id=1.
Best Regards,
Bof