It was recently brought to my attention on IRC that users of OpenJDK for Linux were unable to save nor load designs from my reactor planner.
After a bit of research is was found out that the cause was a bug in an OpenJDK version called "Iced Tea". As a workaround I've added a 'Paste' button that will attempt to read a copied reactor URL from the clipboard.
Saving has been fixed internally, no additional method is needed for Linux users to save designs.
Edit: There's a link to the bug