SetFieldTouched() is used to set the value for the touched flag of the specified fields. The method needs two arguments: the fields list and the flag value:
CALL DIALOG.SetFieldTouched("field_list", value)
There is some specifics about using variables with ui.Dialog methods.
You can learn about them here.
The reference rules for the fields are the same as with the GetFieldTouched() method:
The value can be set as TRUE - to set the fields as touched and FALSE to set them as untouched:
CALL DIALOG.SetFieldTouched("scrrec.*", TRUE)