Rasarnavasudhakara 3.18

3.18

atha patākā-sthānakāni-
aṅgasya ca pradhānasya bhāvyavasthasya sūcakam |
yad āgantuka-bhāvena patākā-sthānakaṃ hi tat ||

Now, the dramatic dramatic indicators (patākāsthānaka):
That which, by way of an accidental occurrence, indicates an element / whether subordinate or principal that is in a future state, is indeed a dramatic indicator.