Thanks for the suggestion! A native Apple Watch app was actually just added in the latest iOS version of WorkingHours.
Please make sure you updated WorkingHours on your iPhone to the latest version and check the Watch app on your iPhone to see if WorkingHours is installed on the Apple Watch. The Apple Watch app is a Pro feature and allows starting, pausing and stopping the timer, including quick task selection.
If you already have the latest version but still do not see the Watch app, please let me know your WorkingHours version, iOS version, watchOS version and Apple Watch model.