The following is a summary of points distilled from discussions from Mirabai Knight and others on the Plover Google group and Discord.
The steno layout was created by Ward Stone Ireland in the 1910’s and his machines were sold by his company the Universal Stenograph Company. It has 22 keys, arranged in a specific order, in three rows and has remained almost unchanged since its invention. The keys are ordered left to right, going top to bottom along each column like below:
The WSI layout is not the only keyboard used for stenography. However, it is likely the one in taught and in widespread use in the United States. There is also the Michela layout (which uses a piano keyboard) and the Velotype. Both these layouts can be used with Plover with additional plugins.
Plover also has custom layout for different languages such as Chinese, French etc.
Alternative keyboard layouts (many) exist for QWERTY layouts, arguing they are more ergonomic, reduce finger travel and decreases spelling errors.
With the exception of the right pinky and index finger (depending on which the write uses to press the \(*\) key), all other fingers travel only in one direction on the steno keyboard, and never diagonally like on a QWERTY keyboard. As a result, the steno write probably has less finger travel than any other keyboard.
With two keys per finger, the hand never leaves the “home row” position, which means almost no hand/wrist movement is necessary.
The key presses from the steno keyboard also will translate through the dictionary before a word is written. So while it is possible to press wrong combinations, Plover will likely always have correct spelling for a word if the correct keys are pressed.
The layout is divided into initial consonants, vowels, and ending consonants.
The T, D, and S keys are at the very end because many words end with such letters (especially in cases of plural and past tense words). link
If you study the steno keyboard layout and steno order, you’ll find loads of places where clever trade-offs have been made. Consider the ‘R’ key on the left side, which is the last consonant (before the vowels) in terms of steno order. Some of the consonants that precede it are frequently combined with ‘R’ in that order, e.g. TR (train, trade, etc.), KR (crawl, crane, etc.), PR (prowl, print, etc.) By contrast, it’s very rare in English to see RT at the start of a word, same for RK and RP. Now consider HR, and try to think of any English words that start with those sounds. There aren’t any! And that’s why the steno keyboard layout uses those two keys as a chord to stand for the letter ‘L’: it’s never ambiguous (did you mean ‘L’ or did you mean ‘HR?’)! Again, the placement of ‘L’ in steno order is well thought out, with some of the consonants that precede it being frequently combined in sequence with ‘L,’ e.g. SL (slow, sleigh, etc.), KL (clever, clown, etc.) PL (plover, plough, etc.).
The entirety of this thread contains a massive effort to generate a new steno order based on phonemes from the CMU dictionary.
The main conclusion is that the computer generated steno orders and the WSI steno order perform highly on writing onsets (initial consonants) and codas (ending consonants). The computer generated steno order does perform better, but purely as steno order, and not as a keyboard layout (which will condense the order to fewer keys and create conflicts). However, none of the new steno orders show massive improvement to justify an effort.