Also, the whole volume of sawdust that you added will first be converted into around 1/4 or maybe 1/2 that volume of fungus, then somehow that fungus will mostly "disappear". After the organics in the sawdust and bagged soil are consumed, the soil surface will subside.
The permanent part of your solution was the sand and mineral portion of the bagged soil.
If I was rich, the first thing I would buy would be a few cubic yards of finely crushed stone (and a team of stout lads to wheelbarrow it around and till it in).
After establishing good drainage and grading over the whole yard, I'd invest in compost. Lots and LOTS of compost.
But neither of us is rich.
It sounds as if merely raking the old soil level would not have solved your problem either, because then the whole bed would have been "below grade" or "sometimes underwater".
I like to dig, so I leap towards solutions like "Make a raised bed out of some of that area (you called it a planter?). Make a sunken pathway out of the low spot (that's where you get the soil to add to your raised part). Dig a slit trench from the lowest spot of your sunken walkway to whatever lower spot you want water to drain down and away to."
That may be too much work or take too many months for most people.
In fact the only solution I know that requires more work would be to re-grade the entire AREA so that low spots are averaged with high spots and the soil surface all drains away (to some lower spot) without any low spots walled off from lower spots.
But most important, whether you like to dig or not, is that every low spot where you DON'T want a pond, needs a way to drain to a LOWER spot.
(I'm used to poorly draining clay and yards that slope at least a little everywhere. I guess that places where soil can drain rapidly straight DOWN, or here are no slopes to work with, need other solutions.)
