It would help users a lot the possibility to have comments on each field giving instructions on how to fill de fields. This is especially necessary in case of complex fields. This feature existed in a now obsolete program called Idealist: you placed the cursor on the field, clicked the right button of the mouse and in the contextual menu could choose to see the comment written by the person who had prepared the database.
Last version of FileMaker certainly has improved the program allowing to write some text that the user sees before beginning to write in the field. But this is not sufficient for two reasons: 1. These instructions disappear as soon as you insert the first character. 2. They cannot be very long.