Please share how and when the knee lift is used. I have it but don't really know why it is so useful!

Needle up/down, large harp, and good lighting

adjustable needle position, zig-zag, needle up / down. I know zig-zag sounds strange but that is the ONLY thing I really miss on my antique machines the others are just added bonuses I have come to rely on

Needle up/down, thread snip, light.

needle up/down, scissors, pressure foot automatically lifts up a bit when stop sewing and automatically goes down when start sewing

You don't need to use your hand to lift the pressure foot, just use your leg/knee.

#1. Needle up/down. #2.Vertical bobbin as it makes it easier for free motion quilting. #3. Longer throat.
Sharon

The knee lift is used for putting the presser foot down hands free, its also very nice when you're doing machine applique and quilting. It makes pivoting much easier. I've had Berninas for 21 years and just love the knee lift feature.
Sharon
Berninas 930 & 1031

walking foot, needle threader, my only needs

Needle up/down, adjustable motor speed, good grip on the feed dogs,

followed by large throat, needle threader, scissors, drop-in bobbin, even blanket stitch, good lighting, and not fussy with threads.