I read once that a vertical cut, part way up a cutting from its base would more likely result in 2 pups per cutting.
I've propagated only 2 leafs and did not do this, but still got 2 pups with both, sprouting from roughly in the middle.

I wonder if planting, or placing in water, only a 1/2" of the variegated part would result in the growth to come from only there.

On one of my leaves, the variegated side was suspended about an 1/8" above the soil and it sent roots out about 1/4" but didn't grow any longer. The buried portion grew normally.
I'm willing to bet you're on to something...

I will do the experiment this coming summer. June/July gives me the best rooting success. Earlier attempts ended with basal rot. That will give me a hint on how wide the slice must be in order to root and give a new pup.

The great sansevieria explorer, collector and author B. Juan Chahinian has drawings in one of his books about how to control where a new growth arises on a variegated leaf cutting. I'll have to check my books to be sure and I'm not home right now, but I believe you cut the green sections vertically from the bottom and then horizontally across so they are shorter than the variegated portions. When you plant the leaf the only parts of the leaf in the rooting mix are variegated. In my experience, new growth from variegated parts are usually albino with no chlorophyll, but as proposed, forcing growth from a piece of leaf where variegation just joins the green is interesting. So you would cut green and variegated sections higher and leave lower portions with an edge of white and green, which would be put in the mix.

If this is clear as mud, let me know and I'll try to explain a different way. Meanwhile, I'll check Juan's drawings and get back if they're different than I've explained.

Russ

Yes, it sounds very much the same. Is it like the illustration below?

Does the green part touch the soil or stay above it? I would like to keep significant green tissue for healthy growth, however, so I guess 50% variegation may still be fine but I wouldn't try to get more than this.

Clarification: i meant to ask if the yellow part is below the soil up to the edge of the green portion

Yeah, to get a plant from the edges where variegated and green tissue come together, you'd have to have both down in the soil mix. Trick is to keep that area fairly small so you don't get wasted leaf energy producing albino offsets from the variegation and plain green ones from that side. So I would keep the width in the mix as small as possible, maybe one inch which would give 1/2 inch for each side. A little narrower might be better to force growth from the division line, but it's trial and error. Obviously you'll have to have a support to keep the leaf vertical with so little tissue in the mix. Sounds like a fun experiment.

Russ