Whiteboard editor
Open a blueprint's .bpex file to see its whiteboards. Download a board as PNG, edit it in any image editor, load it back, and save the new .bpex. Your files never leave your browser.
Where are my blueprint files?
On Windows, in %USERPROFILE%\AppData\LocalLow\ApproximatelyGames\ApproximatelyUp\Blueprints. Each blueprint is a <guid>.bp with a matching .bpmeta (which holds its name) and, if it has whiteboards, a .bpex. Keep a backup before replacing the file.