No need to apologize at all @ben
Thanks for offering your contact details, I really appreciate that. And your video will come in handy too.
I actually managed to get something working by adding a new API that returns all client names and I added a condition to the query where the editor can only view clients that has their warehouse_id.
And to submit the client_id based on the dropdown field, I followed the suggestion in the Disable or Readonly with Select Dropdown post to use the same name and id for both the dropdown and hidden client_id fields.