On Fri, May 18, 2018 at 1:18 AM, Stefan Baur <X2Go-ML-1@baur-itcs.de> wrote:

[...]
The problem arises on systems that have a Window Manager (like OpenBox),
but no task bar, so no way to un-minimize the X2Go/NX-window once the
user hits the magic pixel.

Are you sure that task bar is required? AFAIK any tool with window switching ability (e.g. bbkeys, xdotool, some custom quick-and-dirty libwnck script) would work, wouldn't it?