Thank you for participating in the Samsung Developer Forum. Are you asking this as a developer/designer or as someone that has a Galaxy Watch4?
As a designer you would need to open the battery App I don’t see anyway to get the time remaining information with WFS.
As a developer it may be possible but you’d have to ask on the Android Studio discussions.
But if you are a user, then this is not the correct forum for end product questions
I would recommend you use the Samsung Members App for feedback or post at https://www.samsung.com → Click on Explore Tab → Click on Community.
Because end user questions disrupt developer discussion this thread will be removed at some point.
Samsung Developer Community