Editing a strategy that has already been tested creates a new version rather than overwriting the old one. The previous version keeps its result, so a change you did not like is one click back.
Two ways to change something
Tap a node on the canvas for the parts that have a direct control — the session window, the stop, the target, the position size. Everything else is a sentence in the chat: "make the stop wider", "only trade the London session", "use RSI 21 instead".
Comparing versions
The version picker in the header moves between them, and each version keeps whichever backtest it was run with. A version that has never been tested says so rather than showing the previous version's numbers.
On changing one number at a time
It is the only way to learn anything from a change. If you widen the stop and switch instrument in the same edit, the next result tells you nothing about either.
It is also how strategies get overfitted. Twenty edits chasing a better backtest produces a strategy tuned to one stretch of history, and history is the one period it will never trade in.