A Sell watchlist for a Buy watchlist

I think you are asking for a scan that is based on your current open positions. The watchlist in this case is nothing more than a tool used to store and/or display the output of your scans. Folks can get really confused by interchanging these terms. A watchlist can only display a list of stocks and is not able to generate any alerts or notifications. Only a scan is able to select and display a list of stocks meeting your filter criteria (results list). And a scan is able to generate alerts and notification. So we need to keep those terms separate to make sure folks understand the solution.

If I understand things correctly, what you really need to do is create your own list for Open Positions and use that as the top level filter for the scan that gives you the sell signals. In this way the scan only gives sell signals for stocks you have purchased and currently hold in your account. There is no way to automate the intermediate step of creating and maintaining a watchlist of open positions. Well actually there is but you would have to have all of your trades executed on Thinkorswim. But in either case the solution is to use the watchlist that includes all of your open positions as the top level filter of the scan that generates your sell signals.

If you have any questions about any of the terms I just used (such as "top level filter") the please be sure to take some time to learn everything there is to know about building scans in Thinkorswim.

https://www.hahn-tech.com/thinkorswim-scans-beginner-to-advanced/