I am programming a GravityForm geolocation submission form to get custom coordinates for a database. This form will create a CPT called System. The goal is to have an option within this form to select/connect a different CPT within a relationship called Address. Each address can have multiple Systems.
I don't see that I can utilize custom fields to make this work, so I'm at a loss of what to try next.
Is there any documentation that you are following?
It sounds like you have a one-to-many relationship between Address posts (parent) and System posts (child), and you have a form to publish child posts where you want to link the child System post to a parent Address.
You can include parent fields in Toolset Forms and this is handled automatically, but if you are using Gravity Forms you will need to do it manually.
Your form will need to include a dynamic field from which users can select an address. (If this is a select field, you will want the options to have the address post id as the option value, and the address post title as the label.)
Then, use a hook to run code after the form is submitted (check the Gravity Forms documentation for what they have available). You should have available the ID of the new System post and the ID of the Address post selected in the form, and you can use those to connect the child to the parent using the API function toolset_connect_posts (https://toolset.com/documentation/customizing-sites-using-php/post-relationships-api/#toolset_connect_posts).
If you are unable to do this, you should be able to find a Toolset contractor who could do this for you: https://toolset.com/contractors/
