Note: After saving, you have to bypass your browser's cache to see the changes. Internet Explorer: press Ctrl-F5, Mozilla: hold down Shift while clicking Reload (or press Ctrl-Shift-R), Opera/Konqueror: press F5, Safari: hold down Shift + Alt while clicking Reload, Chrome: hold down Shift while clicking Reload.
.overlay-header {
  position: relative;
  max-width:100vw
}
.header-action {
  position: absolute !important;
  right: 0;
}
.overlay-title {
  max-width: 50vw;
}
.oo-ui-buttonElement-button {
  max-width: 90vw;
}