Setting up a keymap for a Corne split keyboard to be used for data analytics

Continuing my dive into the rabbit hole known as split keyboards, I got a Corne keyboard from YMDK on Amazon.com.  A Corne is an open source keyboard (circuit board and source code are freely available. The original creator is not in the keyboard building and selling business so he lets others improve his design and sell them) It is a 3 row X 6 column + 3 (thumb row) key per side board column staggered board. The goal here is comfort from being able to independently place the halves of the keyboard under my fingers and reduce the need to twist my wrists. (i.e. reduce repetitive strain injury)

The trick with this keyboard is what to do with they symbol and control modifiers. Also known as the keymap. The answer is creating layers, such as the shift layer used for capital letters and the symbols under the number keys. So I have a symbol/navigation layer and a number/mouse control layer.

There are a few general principles I had in making the keyboard.

1. The baseline is the standard QWERTY keyboard. I spent a lifetime building up my muscle memory and I'm not going to throw it away.
2. I wanted to try a numpad on the right side that should also be associated with common math symbols.
3. I wanted VI type navigation keys  (i.e. h, j, k, l correspond to left, down, up, right)
4. Keep the symbols associated with shifted number keys on the top row, in order
5. For symbols that did not make the base layer or the math layer, keep the symbol and the shifted symbol together (shifted symbol below the main one)y
6. As I use it and make mistakes, move characters to the key my fingers wanted them to be.

So, the base layer is as much of the QWERTY layout as could fit.  The left column had tab above escape above shift. I started out with the escape in the corner and tab under it, but clearly my pinky wanted the tab to be next to Q. For the right column, I started out with the backspace next to P and Delete under my thumb, but a bit of use led me to switch them.  The left thumb keys had insert, enter, and lower layer (symbols and navigation), with the insert key doubling as Control when held down (also known as mod-tap). The Enter key doubled as Alt when held. The right thumb keys were raise layer (numpad, math symbols, and mouse control), space (Control when held) and backspace (alt when held). I also set up home row mods, where both hands the home row keys doubled as shift, control, alt, Command when held.  

The lower layer was for symbols and navigation.  The top row had the symbols that would normally be on the shifted number keys.  The left side had the keys that were displaced from the base layer: []{}\|`~.  The right side had the VI arrow keys on h, j, k, l. The row below those where navigation within the row: beginning of row, previous word, next word, end of row. The column to the right had page up and page down. The last column on the right had top and bottom of document (or cell for Jupyter notebooks)

The raise layer was mouse controls, numpad, and math symbols. Left side had mouse controls (left, right, up, down, clicks, scroll) and math logic symbols &|!<>.  Right side was a numpad, with -+/*_= around the numbers.  

The third or adjust layer were to control the keyboard or computer.  Left side was the keyboard, specifically lighting.  Right side were media controls, screen brightness, and screen zoom.

What really made this work was the use of combos.  I made combos (two key combinations) for the bracket type symbols which were mirrored on the left and right sides. This covered <>, (), [], {}.  In the inside columns, I made combos for :, <-, |>, # which are used in R.

Actually, this was a major modification. My initial layout had the numbers along the top row on the raise layer. But while I don't use numbers that much, when I need them I need many of them, and a numpad is less awkward.  I think.  I will know after much more use.

And here are my keyboards.  I have two Corne's, one MX with Akko Dracula (low weight linear) and XDA profile keycaps and a low profile with Kaith low profile silent tactile with low profile MX keycaps.  And a Sofle with Oetemu silent tactile switches and XDA keycaps. The Keychron K12 with Cherry Reds and OEM profile keys is what I was using before as a reference.  The Sofle is used with my work computer (having a number row is useful for making passwords smoother). The low profile Corne is packed in a bandana and a bag for travel. The MX Corne is used for my personal/non-work laptop. Since I got my first Corne in late August, this represents a big dive into the rabbit hole of split keyboards. 

For tenting, the Sofle has M5 bolts that came with it from Ergomech, the low profile Corne is using Steepy laptop risers which is what I take when out and about.  And the MX Corne is on Cooper Cases MagSafe stands.