Apple today pushed the watchOS 10 Developer Preview Beta 7 update (build number: 21R5349b) to Apple Watch users. This update is 6 days after the last release.

Judging from Apple’s update instructions, this version is mainly a bug fix, and optimizes the charging limit for Apple Watch SE, Series 6, Series 7, and Series 8, allowing Apple Watch Series 6 (40mm) to more accurately estimate the maximum battery capacity.
watchOS 10 adds a new widget-centric interface. You can use the Digital Crown to switch from any watch face to the widget stack, swiping through them to get relevant information. Control Center can be activated from any app by pressing the side button.
watchOS 10 also has new colour palettes and Snoopy watch faces, cycling and hiking updates, and mental health integration. Users can use the Apple Watch to record their state of mind and emotions, and the device provides mental health insights over time.