Turn out to be very old WM configuration files from the ancient history
of this "host". When removed and rebooted the problem went away. Whilst
the system was a new installation, the inherited user files contained
historial data.

On Sat, 26 Jan 2019 10:36:02 +1100
terryc <terryc@???> wrote:

> I've just assembled a new machine and intalled Devuan Ascii
> from devuan_ascii_2.0.0_amd64_dvd-1.iso with update and upgrade from
> pkgmanager.
>
> The desktop is XFCE4 and the first installation user can create
> desktop icons/launchers and have then run/start, but the added second
> user can not achieve similar success.
>
> The icon/launcher can be entered but it fails to launch and
> gives a general multipart message of reasons for error, of which the
> only relevant part is something about "policy".
>