I like that it is online. Often, when you need a quick sketch for your presentation or colleges, you don't want to open a desktop tool (you might not even have).

I would appreciate drag-able interface on the right (I know it is hard but it would definitely be a plus).

Connect a git repo or gist would be also nice.

I've also seen integrations to Google Drive where you can store it as a document.

Do you have any further plans with this tool? Cover more UML diagrams and so.

Thanks for the feedback! Diagram is not drag-able but support inline editing with double click. Google Drive integration is in the works. Gitbook plugin available: https://plugins.gitbook.com/plugin/swimlanes-io. Had the initial ambition to support flowcharts but want to ace sequence diagrams first