I have an Elna 740 and it has a dual feed feature that you can engage by using the dual feed foot and engaging a piece that's on the upper level. It comes from behind the needle to attach and it engages easily and works well.
What I don't like about it is that you have to attach/detach special feet to use the dual feed which makes the easy change foot option of the regular foot clamp not usable - if that makes sense to you?
To use the dual feed feature, you remove the regular piece that screws to the needle bar and replace it with a one piece foot that is either a "regular" foot with an open mouth so you can use straight or zig zag or decorative stitches, or a quarter inch or stitch in the ditch foot.