Expanding a connection node down to the column names and then right clicking a column name and then Properties opens a dialog box with several tabs.
The only property that applies to API is on the CRUD Options tab: Part of Unique key. This option applies to autogenerating API and Modules. See Build API & Build Module.
The rest of the properties apply to creating Profound JS Rich Display Screens if you have a Profound JS license. For more information see CRUD Generator.