In Abstract, you can create a separate project for each Kit and then have a branch for each component. Designers can tag a component that’s in progress with “In Progress” or “For Review” and then merge it later with the master branch, which adds it to the final sketch file.
…disorganised assets in several places? Or not knowing who made what edit to a file and when or why? As far as I can tell, collaboration within tools like Zeplin or InVision seems to be limited to commenting on screen mockups. It does not allow your teammates to make changes and submit them as suggestions (like a “pull request” in development).