You can import not only completed games, but even templates that can be more or less at a finished state or just a little example.
The Asset Store has both.
Here for example you can see a template I made for an horizontal shooter in 8-bit style:
https://www.construct.net/en/game-assets/game-templates/8-bit-pixel-art-shooter-361
You can try it in the Arcade:
https://www.construct.net/en/free-online-games/test-demo-8-bit-pixel-art-4962/play
Here instead I have created a template for a First Person Shooter on Rails:
https://www.construct.net/en/game-assets/game-templates/fps-rails-template-363
You can try this too:
https://www.construct.net/en/free-online-games/test-demo-fps-rails-template-4963/play
You can also have a look at bundles, for example, I have joined here other creators in order to offer at a discounted price many different types of templates for games:
https://www.construct.net/en/game-assets/bundles/top-assorted-construct-71