Hi @swisskud ,
Thanks for getting in touch about this. To add an additional checkbox custom field to your WordPress form, you have a few different options:
1) Within the plugin you can choose “Create New Field” and click the add button: https://cm.d.pr/N4n8Dr
Give your field a name, and make it a required “Multi Select Many” field with only one option: https://cm.d.pr/fmXkKe
2) Alternatively, you could first create the “Multiple options (can select many)” custom field in Campaign Monitor first. Then when creating your WordPress form, you should be able to select?that custom field from the same “Create New Field” dropdown, as seen here: https://cm.d.pr/5iiDe6
Note that you’ll have to select the Client and List first in order for the custom field options to appear.
If you’re not seeing your custom field showing up in that dropdown, could you please try Deactivating the plugin under the WordPress plugins menu, and then re-activating it, to see if that resolves the issue?
Please let me know if this works for you.