By default devtools seem to be well hidden if menu bar is hidden too. They should be in the hamburger button by default, I think.
Ux made a careful and deliberate choice as to which widgets are supposed to be in the default, user-facing set for the menupanel. We're trying to make the layout as easy to customize as possible, so putting the devtools widget in there should be trivial for devs who want it there.
Duping forward since there is more discussion on this.