Store state in local storage/db

[seasick]

Is your feature request related to a problem? Please describe.

I automatically press F5 to render a preview. If I do that in the web interface, then my changes are lost.

Describe the solution you'd like
While F5 might be able to be supressed, I think the better approach would be to store the state in local storage. This way I don't interfere with the browsers refresh functionality.