Hi, Magnus
You can follow the next steps to achieve your request.
1. Add the subscription lists into Marketing Page instead of Market Form. You can add them into Marketing Form first and then cut them into the HTML of the Marketing Page.

2. Add a consent checkbox which you’d like to control all the subscription lists.

3. Add a JavaScript function to the consent checkbox which is under the script ’ function (id, f, t, ws, ms_tr_il_08, ms_tr_il_w_01)’


Then you can use only one checkbox for marketing consent in a Marketing Form for all or a few of their Subscription lists.

Hope this will help you.
Regards,
Clofly