Help to show and manage multivalue / json user attribute in account console

Hello there, KeyCloak newbie.

I’ve configured my first keycloak protected web-api in C# NET 5.0 and works flawlessly.
Here the question: I should create a custom user attribute called “Databases” which should contain multiple values (in this case the databases an user could connect and then checked in my own API)

Reading around I have 2 possibilities:

  • Create a multiple value attribute
  • Create a JSON attribute
    Is there a way to achieve this? I see for adding user attributes with multiple values in account console is something like this

value1##value2

Is there a way with freemaker to make a grid and then save a multiple value or json value correct but in GUI show a grid? Or I should use the admin API and make my own interface with C#?

thank you.