Currently we do not have dynamic fields (e. g. input fields that do not have a connection to an existing attribute) - but you can use frontend functions to fill a pre-existing input field with values of other fields (or values from backend functions or whatever else).
So in your example, you would have 3 attributes (
displayname) - all 3 placed as input fields on a form, with the last one set as readonly and filled via frontend function from the combined inputs of the first two.
This only works with input fields though - for tables we currently do not have any methods to access the data in there. In this case you´d have to store the calculated value in the DB to be displayed in a table.
The reason we used a trigger in
Organizations, is that we very often need to show/access the display name of contacts, so it makes sense to not only calculate it on a form, but to have it directly in the DB ready to be used in any context.