[tpmoney]

I didn't like the default layouts for symbols either and wound up building this layout[1] (there have been a few minor tweaks since but nothing substantial). The parens as double taps on the shift keys is the big one for me for writing code. The other brackets on the inside are convenient enough to use but not occupying "prime" space, and I have "auto-shift" enabled so a top on "[" give that character, but holding it down (for > 160ms) gives "{" (and same for all the other keys and their respective shifted versions. And in case it isn't clear what's going on in the thumb clusters, the two enter keys and the space key do their respective actions on tap, and do Left CTRL, ALT or Right CTRL respectively when held down. Might be a place to start if you wanted to try again.

Also on the "muscle memory" thing, I decided early on to not try to modify any other keyboards in my life. Just the ergodox get the middlemak and super custom layout. I found that preserves muscle memory for laptop built in keyboards and using other people's and allows my brain to form a completely separate set of muscle memory that kicks in on the ergodox and neither seem to conflict with each other. Works for my brain, might work for you too.

[1]: https://configure.zsa.io/ergodox-ez-st/layouts/wzKWq/latest/...