Thanks for your answer. I am almost there.
So it was simpler than expected. I declared dynamic fields in my form, that I linked to the following method:
membership = $evm.root['dialog_param_user_membership']
case membership
when 'Revoked'
status = 'None'
membership_value = 1
when 'Administrator'
status = 'Administrator'
membership_value = 4
end
list_values = {
'required' => true,
'values' => {1 => 'None', 2 => 'Guest', 3 => 'User', 4 => 'Administrator'},
'value' => membership_value,
'read_only' => true
}
list_values.each do |key, value|
$evm.object[key] = value
end
And I get the following result:

I know it looks like my previous screenshot
but actually this one is fully dynamic whereas the previous one was static.
I think my declaration is not correct:
membership = $evm.root['dialog_param_user_membership']
How can I get the value of my radio button selected by the user?