Configuring your process model start forms and user input task forms via an in-line expression has been deprecated. The Write an expression option will be removed from the Process Start Form tab and the Forms tab in a future release of Appian.
Instead of configuring a form via an expression, directly select an interface and map inputs to your process variables. For more information, see:
Any start form or user input task that was previously configured as an expression will continue to work as expected.
For information about using expression-backed forms for Appian 21.2 and earlier, see the Appian 21.2 documentation, for example, Process Model Object.
Write a Form as Expression in Process Models [Deprecated]