Hi Paul Chou,
Thanks for sharing the build number. Since you’re running build 26340.9616, the Battery Status widget should be available under the Widgets board. Press Windows key + W, select Add widgets, then look for Battery Status and add it from there.
If it isn’t showing, could you let me know whether the Widgets board opens and works normally and whether Battery Status is completely missing from the widget list?
I’d also try restarting the PC, checking Settings > Windows Update for any remaining updates, and opening the Store to Library > Check for updates to update the Windows Web Experience Pack. After that, open the Widgets board and check again.
If it’s still missing, the feature may not have been enabled for your device yet, as some Insider features are introduced gradually.
Please let me know how it goes.