Update dynamic columns mariaDB

I am trying to add a todo list feature where the user can update or add new data to a dynamic column BLOB in mariadb. They select the experiment they want to see the todo list for which generates in the todolist table. I have having some issues writing the update and insert statements and am getting a “experimentID does not exist in the array” error. Any ideas on how to do this?

this is mariadb’s docs on dynamic cols