How to build a personalized system?

I am building a web application using flask and I would like to build a system that allows add new columns by the user or the administrator, we need to use this system by multiple clients so sometimes we want to share some functions but it can be a different code depending from every client also every update is going to affect every system, and there can be only one web project (code) and an api, we use mysql for the database and finally we want to use okta and I noticed that the users list is showing between every application that you create in okta developers.