We, at Kaleyra Designs, currently follow Ship-Show-Ask format for Design System Branching. We keep Design Decision Log, and use Changelog as a consistent communication tool.
For Ship, designer directly merge it to design system, and take care of feedbacks. If it’s more complicated, the change will be added (and show) as a variant, and will clean up as we have more clarity. If the sophistication and impacts are high, we save it a s a new component, and discuss it in our bi-weekly ‘Ask’ meetings.