Backwards outside edges

I'm not quite there yet myself, doing backwards crossovers, but I can tell you how figure skating lessons work up to backwards crossovers—maybe you can find something useful there. I guess though that these work best if you have a somewhat maneuverable frame (short, possibly rockered).

Start with backwards half-swizzles/half-lemons on a circle: https://www.youtube.com/watch?v=J6I_IN65_tM

This teaches you to stay on the outside edge with your inner leg while your other leg moves. (That's where I am myself, and it works on inline skates just the same.)

Then you can extend that so that you bring the pumping foot in front of the inner foot, and then even more inwards so that you do basically a half criss-cross. (Btw, I think criss-crosses on a straight are also a neat exercise for crossovers.) If you can do that and bring your outer foot comfortably over to the inside without lifting, you can start to lift your back foot, see here: https://www.youtube.com/watch?v=pPme7Hs6tlM

You can also do crossover steps in place for a bit, like how she starts out here, maybe even on grass: https://www.youtube.com/watch?v=3iOqaiKEv6k (She also goes directly from the swizzle pumps to lifting the front leg over. It comes down to personal preference if people start with lifting the front leg or leaving it on the ground.)

For skating backward I used this video. https://youtu.be/gpP5N2MofsI

I learned backwards outside edges for crossovers doing a figure of eight pattern/infinite loop ♾

It forces your mind to adjust to using the side which you’re weakest on when switching directions.

Keep on doing this pattern and you will get better.

no one didn’t have to go through a ample learning curve in order to learn to skate backwards, including backwards crossovers of course, which are difficult not only because they require that the backwards skating feels natural but being able to go backwards putting the weight on one foot, and like you suggest, not vertically but inclined and with the skate on its outside edge.

it’s good to recognize these are difficult skills, so in this way you can lower your anxiety. don’t feel that you are struggling, you are learning movements that are not natural to anyone’s body, so it will take time, which you have.

in my opinion one foot skating in general is necessary to do backwards crossovers, and the skill progression for skating with one foot is: dominant foot forward, switch foot forward, dominant foot backwards, switch foot backwards. i find that confortable backwards crossovers goe in hand with comfortable one foot skating, forward but of course more especially backwards.

so my advice is to include one foot skating in you practice, first centered on your skate and then looking for both edges (snaking the skating), forward and backwards, dominant and switch.