The navigation subscreen title and position text are set by the view cluster maintenance transaction to Navigation by default. Using function module VIEWCLUSTER_SET_SUBSCREEN_TITL you can modify the navigation subscreen titel and the position text Level 1 of....
Create a FORM routine that calls function module VIEWCLUSTER_SET_SUBSCREEN_TITL.
Pass the the navigation subscreen title and position text as export parameters to your FORM routine.
Enter the FORM routine at event 01.
Modification of the navigation subscreen title:
CALL FUNCTION 'VIEWCLUSTER_SET_SUBSCREEN_TITL' EXPORTING SUBSCREEN_TITLE = 'Neuer Titel' POSITION_TEXT = 'Eintrag' EXCEPTIONS OTHERS = 1.