Finally after finding some spare time, I was able to move to Joomla 3.6...
So unfortunately as I cannot maintain anymore the "Bookmarks" Component, I had to find a replacement.
Well the component "MosetTree" seems to fulfill my needs, and works fine with this latest version of Joomla...
Some feature are missing as I still have to install never version or to convert them to be compliant with J3.6.
Thank for your patience.