को धर्मः पूर्वोक्तलक्षणः सर्वधर्माणां सर्वेषां धर्माणां
In plain words
Which dharma? The one whose defining mark was already given earlier. And sarvadharmāṇām — read it as two words: of all, of dharmas.
Close to the Sanskrit
Which dharma? The one whose defining mark has been stated earlier. 'Of all dharmas' — of all, of dharmas.