Short answer
The ▾ next to "Download PNG" has Export .drawio. Open that file in draw.io and you get a Mermaid shape you can double-click to keep editing the code — the export uses the same structure draw.io itself writes when you insert Mermaid, with the source stored on the shape.
And back again
Drop a .drawio or .drawio.svg file onto "Open file" in the top bar (or paste its contents) and every Mermaid source inside comes back out; if there are several, you pick one. Compressed and uncompressed draw.io files both work.
When the round trip is worth it
- Your team's diagrams live in draw.io and this one has to join them
- You need the diagram on one canvas with other shapes, frames or a legend — that's what a canvas tool is for (for circling, arrows and short notes, “Annotate” in the preview's top-left corner is enough)
One boundary to know
Once a diagram moves to draw.io, edits there don't come back to the code. The code stays the source of truth here, so the order that works is: get the structure right here, then export for final layout.
Try it
flowchart LR
A[Backlog] --> B[This cycle]
B --> C[Design]
C --> D[Build]
D --> E[Release]
E --> F[Retro]
F --> AEdit the text, switch themes and download PNG, Word or PowerPoint from there.