Thanks to you, I doubt I’ll have more examples: now that I’m aware of this limitation, I’ll just not get into this situation.
As silly as this example was, it was real. Every tool has different workflows. In Illustrator for example, the fastest way would be to create the basic shapes and then use the shape builder to trim the middle. This would also allow me to get the buttons separated without having to make the shapes separately. In autocad or similar, I’d use a mirror line and then a trim command. In gravit… better to avoid this by drawing two separate lines it seems.