Is this what you looking for? The side treads you can make it uniform or whatever distance you want to extend it. Don't forget to remove the tread thickness from the last step at the bottom

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Your ideas for stairs will make for an uncomfortable, and possibly dangerous, gait. Follow the rules, please.

Thank you for the comments. The uncomfortable, dangerous gait is what I am trying to avoid. What if, instead of the design in the original, I had more standard sized steps with a larger landing in the middle.

From the deck surface there would 4 total steps each with a 6 inch rise. The first step down would be onto an 11 inch deep tread. Then a step down to a landing 36 inches deep. Then two steps down, onto the ground with the tread depth at 11 inches.

How would that be for both safety and aesthetics?

Why you driving yourself crazy.

You will have 3 steps + deck landing...Just build a regular set of stairs make them wider and you will have a comfortable stairway.

I probably should. I am trying to get the stair to end at the edge of the garden bed, for looks and scale. But if it won't work then it won't work.

For comfortable proportioning of exterior stairs the guideline ratio is 2R + T = 24-26", where R is the riser height and T is the tread depth. This works well for the average stride of most people.

If you are introducing landings, these should be long enough to allow for an average stride length, so landings are typically about 5' (or multiples of that).

GN - Does the 20 in tread depth make for a safe and comfortable step?

saccharum, does that formula still hold true with short risers?, in this case a 4.80 inch riser and 15 inch tread?

Yes, that's the guideline for any outdoor steps (keyword being guideline). Recommended riser heights range from 4-6", although up to 7" is OK if absolutely necessary. Anything less than 4" can be a trip hazard.

Here is the mock up I made with 6" riser and 20" tread to see if it felt comfortable to walk up and down. It felt just fine and not awkward at all. I think 5' is a little too deep overall. 4.5' might be a little better.

Why would it feel awkward, it's a comfortable stair layout. If your total rise is 24"/3 it will give you 8" rise, for NJ code you allowed to have an 8 1/4" rise but most places it's 7 3/4"... so you divide by 4 that gives you a 6" rise which is a normal comfortable stair rise especially for the type of stairs you want to build.

The minimum tread depth per code is 9" and there is no max for it.

That said, when you lower the rise below 6" you always extend the tread depth, which is a common way of doing it, so there is nothing wrong with a 20" tread... and after 11" tread depth you not required to have a nosing per code.

If you think about it... the more you drop the rise and the more you extend the tread you end up with a ramp and walking up the ramp is more comfortable than climbing stairs.

Good luck

Some of the most comfortable steps I've ever traversed are in our new mall. 7" rise(+-) with a 14" tread. It's a perfect gait. 20" is too much. Do you take two steps per tread? What about a child?

For a child is even more comfortable, as the stairs in the malls go, that is a typical rise and tread depth because they follow a different code compliance, they follow International Building Code where stair riser heights shall be 7" maximum and 4 inches minimum. Stair tread depth shall be 11 inches minimum.