Hi Franck,
Visual Dialplan for Elastix keeps the VDP file at the following location:
/usr/local/apstel/vdp-pbx/wshome.default.vdp
If you want to move the file to be used in desktop version (Visual Dialplan Professional), just download the file to your desktop, rename it and open it in Visual Dialplan Professional.
If you want to move VDP file developed with desktop version, upload it to server, rename it and place it in the above folder.
Best regards,
Daniel