Hi @linusf,
For future “premium” extension queries, please refer to the forum welcome first. Because this answer won’t be promoting the extension, I feel confident replying regardless.
I believe you can achieve this extraneous behavior by setting the “main” department type to “disabled”.
However, it was never intended to be used for decoupled business directories; it is meant to be used for one single brand of business(es). And as such, I advise not using the extension for this, as the behavior can change in the future.
Instead, I recommend using a dedicated directory plugin for this which offers “localBusiness” Schema.org output as a sustainable alternative.
Best of luck ??
P.S. Please don’t follow up here. Instead, use the discussed channels I linked to in the forum welcome. Thanks!