The Win Switch menu appears to offer the last choice in the .desktop file these typically appear to be the unity specific options which would normally be ignored / hidden in other environments. The files can of course be copied and modified which clears up the problem. It would of course be nice if the relevant parser could be adjusted to take the 1st option in the file (which is the default option AFAIK).

e.g.

Exert from the firefox.desktop file...

From the beginning of the file

[Desktop Entry]
Version=1.0
Name=Firefox Web Browser
....
Exec=firefox %u

The Win Switch menu shows the last option however....

From the end of the file

[Desktop Action NewPrivateWindow]
Name=Open a New Private Window
...
Exec=firefox -private-window
OnlyShowIn=Unity;

If you try to start an application on a Fedora 24 server using WindowSwitch? 0.12.21, you get the following error dialog:

You have requested an xpra session but this server does not support it.

Attempting to start an xpra session directly using: xpra start ssh:localhost:100 --start-child=xchat

actually produces an application.

xpra is installed in the same location that winswitch thinks it is.

When the client connects to the server, there are port forwarding and application startup errors.

[II] 2018/13/04 09:38:53.375532 ConchConnection.forward_port(12497,127.0.0.1,24065)
[II] 2018/13/04 09:39:31.742001 WinSwitchApplet.do_start_session(ServerConfig(desktop:158515233878749),Command(Mousepad: mousepad %F),xpra,None,{},False)
[II] 2018/13/04 09:39:31.742075 WinSwitchApplet.attention(Starting Mousepad,None)
[II] 2018/13/04 09:39:31.742134 StatusIconTray.animate_status_icon(Starting Mousepad,5) now=1523601571.74, tray_widget_animate_until=1523601505.56
[II] 2018/13/04 09:39:31.908503 ServerLink.add_port_forward(None,127.0.0.1,15071) adding new port forward
[II] 2018/13/04 09:39:31.908637 ConchConnection.forward_port(12498,127.0.0.1,15071)
[II] 2018/13/04 09:39:35.937471 ServerLineConnection.do_message(9e007000aad84b759b6f03735717ba4d,Session Mousepad Failed,Session failed to start,)
[II] 2018/13/04 09:39:54.238773 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(Gscriptor: gscriptor)) missing icon!
[II] 2018/13/04 09:39:54.239043 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(Jaxx: "/home/username/cryptowallets/jaxx-1.3.13-x86_64.AppImage" %U)) missing icon!
[II] 2018/13/04 09:39:54.240210 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(TurboVNC Viewer: /opt/TurboVNC/bin/vncviewer)) missing icon!
[II] 2018/13/04 09:39:54.241673 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(OpenCity: opencity)) missing icon!
[II] 2018/13/04 09:39:54.247141 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(aMule: amule %u)) missing icon!
[II] 2018/13/04 09:39:54.251555 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(Power Manager: xfce4-power-manager-settings)) missing icon!
[II] 2018/13/04 09:39:54.252573 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(TeXdoctk: texdoctk)) missing icon!
[II] 2018/13/04 09:39:54.253640 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(PyCrust: pycrust)) missing icon!
[II] 2018/13/04 09:39:54.255005 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(LMMS: env QT_X11_NO_NATIVE_MENUBAR=1 lmms %f)) missing icon!
[II] 2018/13/04 09:39:54.257128 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(GAdmin-Rsync: su-to-root -X -c /usr/sbin/gadmin-rsync)) missing icon!
[II] 2018/13/04 09:39:54.257361 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(GSmartControl: "/usr/bin/gsmartcontrol-root")) missing icon!
[II] 2018/13/04 09:39:54.259273 UI_Util.get_command_menu_entry(ServerConfig(desktop:158515233878749),Command(UNetbootin: /usr/bin/unetbootin)) missing icon!
[II] 2018/13/04 09:39:54.287996 WinSwitchApplet.do_start_session(ServerConfig(desktop:158515233878749),Desktop(Xfce Session: startxfce4),vnc,None,{},False)
[II] 2018/13/04 09:39:54.288073 WinSwitchApplet.attention(Starting Xfce Session,None)
[II] 2018/13/04 09:39:54.288128 StatusIconTray.animate_status_icon(Starting Xfce Session,5) now=1523601594.29, tray_widget_animate_until=1523601576.74
[II] 2018/13/04 09:39:54.547923 ServerLink.add_port_forward(None,127.0.0.1,16072) adding new port forward
[II] 2018/13/04 09:39:54.548147 ConchConnection.forward_port(12499,127.0.0.1,16072)
[II] 2018/13/04 09:39:55.599431 ProtocolHandler.do_encrypted_command(78296cadaa664db4903f9daf30f421f5e745774aa2ab268880acc074aa64e8b4be461c80a2b4e9d6cb5be604d2dc6d8d7...) decrypted command=send_session '4011ea7ccbbf4b4caa82f47d86bb0b98','9e007000aad84b759b6f03735717ba4d','base64:N2UyNGMwMmE= '
[II] 2018/13/04 09:39:55.599610 VNCClientUtil.attach(ServerConfig(desktop:158515233878749),ClientSession(:71 - vnc - connecting),127.0.0.1,12499)
[II] 2018/13/04 09:39:55.625427 VNCClientUtil.do_real_attach(ServerConfig(desktop:158515233878749),ClientSession(:71 - vnc - connecting),127.0.0.1,12499) saved password '#######' in /home/username/.winswitch/client/sessions/4011ea7ccbbf4b4caa82f47d86bb0b98/session.pass
[II] 2018/13/04 09:39:55.625532 VNCClientUtil.exec_client(ServerConfig(desktop:158515233878749),ClientSession(:71 - vnc - connecting),['/usr/bin/vncviewer', 'PasswordFile=/home/username/.winswitch/client/sessions/4011ea7ccbbf4b4caa82f47d86bb0b98/session.pass', 'name=Xfce Session on desktop', '127.0.0.1::12499'],None,None,available,True) starting SimpleLineProcess
[II] 2018/13/04 09:39:55.634440 VNCClientUtil.started(<winswitch.util.process_util.SimpleLineProcess instance at 0x7f5abbdf4dd0>) pid=None
[II] 2018/13/04 09:39:55.634966 SimpleLineProcess.start() process(['/usr/bin/vncviewer', 'PasswordFile=/home/username/.winswitch/client/sessions/4011ea7ccbbf4b4caa82f47d86bb0b98/session.pass', 'name=Xfce Session on desktop', '127.0.0.1::12499'])=<Process pid=6419 status=-1>
[II] 2018/13/04 09:39:56.214816 PortForwardChannel.__init__(<winswitch.net.conch_util.ConchConnection instance at 0x7f5ac06b5b48>,<function forwarding_ready at 0x7f5abbdd7578>,<function forwarding_failed at 0x7f5abbdd7aa0>)
[II] 2018/13/04 09:39:56.214968 ConchConnection.openChannel(<winswitch.net.conch_util.PortForwardChannel instance at 0x7f5abbdf4758>,'\x00\x00\x00\t127.0.0.1\x00\x00>\xc8\x00\x00\x00\t127.0.0.1\x00\x00\xcf\xde')
[II] 2018/13/04 09:39:56.215638 VNCClientUtil.handle_line_connected(ClientSession(:71 - vnc - connecting), CConn:       connected to host 127.0.0.1 port 12499) ServerConfig(desktop:158515233878749)
[II] 2018/13/04 09:39:56.215699 WinSwitchApplet.update_session_status(ServerConfig(desktop:158515233878749),ClientSession(:71 - vnc - connecting),connected)
[II] 2018/13/04 09:39:56.243185 ServerLink.forwarding_ready()