URL from WordPress Import are not the same
You can rebuild the app, it’s built with Electron. The WXR importer code is easy to read. All it needs to do is to read a field from your WXR/XML file. I manually edited the slugs but I had 43 posts, not 400, to edit.
That the slugs don’t allow slashes is annoying since it means you need to set up redirection if you’ve used a path pattern such as/topic/year/title – which is common. I solved it by replacing slashes with underscores, used that as a slug and then set up a rewrite rule to redirect traffic to the old paths.