for the moment I only have one problem : each time I try to resize an imported image or an object I can’t keep the aspect ratio.
The lock proportion option is enable in the tool panel and I’ve tried alt, ctrl and shift keys too.
I’m sure I missed something but I don’t know what.
When I import vectors into Synfig, I often use a Zoom layer to resize them rather than resizing them on the stage.
(New Layer > Transform > Zoom)
However I use the Scale tool on the toolbox to make sure I scale things on the stage correctly. There is a “Lock Aspect Ratio” check box that appears in the Tool Options than ensures that aspect ratio is respected.
EDIT: Make sure you select all the ducks using Ctrl-A first.