Qt Wayland doesn't support window minimizations due to an upstream (temporary) shortcoming but that's now being addressed through the forthcoming XDG-Shell work. The XDG-Shell protocol work is being driven by Wayland developers plus stakeholders from most all of the major Linux desktop environments, though it's not yet part of the stable Wayland API.
With the now-merged patches, XDG-Shell is used by Qt Wayland when available (Wayland 1.5+) so it can support minimization (hide/window showing). For those Wayland enthusiasts and developers interested in learning more, see this Qt bug report. Embedded below is also a demo video with the new support.