I'm pretty new to GA, so forgive me if this seems obvious. Also, I am not the GA admin, that is someone else.
I have written a user registration form in a WP plugin that registers users via an API to our CRM - these are not WP users being registered.
Our marketing department have asked me to also submit a GA custom dimension with the form so it can be cross-referenced in our CRM.
Looking over the GA API, I can't seem to find a way to simply 'get' the current value of the requested custom dimension, only 'create', 'set' and 'send'.
Any advice on this would be helpful - and don't be afraid to "dumb it down", or point to a section on the GA support forums!
You can't easily get the value from GA and send it to your CRM.
I think for your use case you need to look at it the other way around.
You want to get the submission ID from the CRM on the "thank you" page and "send" it to GA in a custom dimension.