Set simple default value
If you always want a certain default value to be displayed for an unassigned user-defined field, e.g. the string "No input available", enter this string in the formula editor.
For example, you could also store the current date as the default value in a user-defined field of the type "Date". To do this, you would have to enter the function today in the formula editor. If an unassigned date field is then accessed in an evaluation, the default value formula returns the current date.