Welcome to Dhan community. Interoperability of watchlists or rather scrips in 2 platforms is very difficult to achieve. We have no idea on the logic someone may have in their scripmaster and we will have one that is different and made as per our usage and also of our trading systems.
We have over time received many requests for bulk uploads via Excel or CSV, and we have tried this as well. The match-rates are extremely low and it will turn up being a bad user experience for our users.
We are building things to get going on this. Like we recently introduced fast navigations widgets where we let you add scrips to watchlists or baskets: Fast Navigations in Dhan Web Trading Console. Also have given option to add Puts / Calls directly from Option Chain and also introduced major indices on TradingView console at tv.dhan.co.
There are more such enhancements planned on Dhan.