Hi! I am working with a PRO plan, in the past I have worked with advanced and higher plans and always worked by sharing cases from the organization structure. I find that this team works by sharing cases between groups, which seems to me a bit less organized than working on the organization structure (using the locations). I have tried to configure the owner_id from the registration form, first using hidden calculations as seen in the image (gives me an error) and then following the instructions in this link: Assigning cases to one of multiple groups - CommCare Public - CommCare Public and it simply does not allow other users in the same location to see the cases created by different users to follow up. I haven't done this setup in a long time, maybe I'm missing something or maybe it's the type of plan (pro) I'm working on now?
That link you shared describes how to choose which group to assign cases to (useful when passing a case from one group to another). Instead, it sounds like your project may want to always assign cases directly to the user's group, so other users in that same group can also see them. Is that correct? If so, then I think this is the workflow you're looking for:
https://confluence.dimagi.com/display/commcarepublic/Case+Sharing