This release substantially improves floating bus emulation for the ZX Spectrum.For macOS users it also:

• introduces a new vertically-oriented machine picker; and
• resolves a long-standing bug in which machines with activity indicators would start with focus in the wrong window.

I think sticking with the existing tabbed machine picker for Qt is the right call; unlike Cocoa, Qt permits its tabs to scroll horizontally. They're also smaller, making for less of an issue.