Using `window.alert()` for error messages is not user-friendly and blocks the UI. Consider using inline error messages, toasts, or other non-blocking notification mechanisms. This applies to both error cases here:

[torleifhalseth]

Using window.alert() for error messages is not user-friendly and blocks the UI. Consider using inline error messages, toasts, or other non-blocking notification mechanisms. This applies to both error cases here:

1. Duplicate step validation (line 392)
2. Maximum anchors validation (line 411)

The comments on lines 390-391 and 409-410 already acknowledge this should be improved, but it's important to address for better UX.

Originally posted by @Copilot in #4247 (comment)