Hello H.,
In order to mix "double lines separator" and "folder", You can use embedded diagram or sub-diagram with use of '{{' and '}}':
But pay attention to the fact: what you gain with, you also lose with (because it is an independent sub-diagram [without any link with the hosted diagram]) ; Also You can not use after DBT1, DBT2 or DBTN, there are only accessible on the sub-diagram.
See more details:
Then with this feature:
database DB [
DB
--
==
{{
folder "Table #1" as DBT1
}}
==
{{
folder "Table #2" as DBT2
}}
--
{{
folder "Table #N" as DBTN
}}
]
we obtain:
We observe some issue (on v1.2020.10) with the order of the element between the sub-diagram and the different double lines (a dummy line above is necessary to achieve the expected result.): see also this defect /10967.
If that can help,
Regards,
Th.