Hello @Martin321
Welcome to the community and thanks for trying Backendless out!
The UI Components is a new feature and we are still working to improve this.
There are lots of improvements in our roadmap, however, you already can create your own custom component (with 3rd libs), just create a new component based on Highcharts Demo template and you will see how it works with an external library
Since the UI-Builder is based on React you can use react components without extra importing React.
Also, we are about to release the publishing/installing components using our Marketplace, so it’s going to add an ability to share components between developers/apps/containers/etc.
Regards, Vlad