When opening the Profile Editor window, if the JVM arguments field is long enough to exceed the monitor width, the window will span multiple monitors to accomodate. Ideally, the window shouldn't expand past the edge of the screen it's on, even if that means the entire text won't be shown.
Sidenote: I would have marked this issue as Improvement, but it's impossible to do so.
Is this still a concern in the current Minecraft Launcher version 2.0.805 / 2.0.806? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. It will be reopened it as soon as the requested information has been delivered.