Thanks for reaching out. I’m afraid this feature is not available in our Linky template. I’d like to provide exact solutions on this matter, but template customization is beyond our support services, unfortunately. But the idea is that you need to have database objects for your category types and connections as well. And when you write a message or send the connection per se, it is going to be registered in your database so you’ll be able to use it later on like for approval on other user’s side, filter on search or any other implementation.
For Bubble help, it is best to post your request here https://forum.bubble.io/.
Hope it helps.