Indian Railway Catering & Tourism Corporation [IRCTC] — feature missing: not able to change boarding station to c when booking ticket from station a to b on irctc next gen site.

I checked seat availability in irctc next gen site from akola jn (Ak) to chennai central (Mas) but seats are not available, then i check from surat to chennai central (Mas), there seats are available.

Now i want to book ticket from surat (St) to chennai central (Mas) but want to boarding at akola jn (Ak) but i didn't see any provision to change boarding station on irctc next gen site.