Muscle memory is generally a useful phenomenon, as it enables you to do things such as touch typing or playing a musical instrument with little or no conscious thought as to what your fingers (or other appendages, though at the moment I’m specifically thinking of digital muscle memories) are doing.
I’m not sure how much it’s actually the muscles themselves that get used to how they should be moving and how much it’s the brain subconsciously serving up the information as it’s required. I suspect it’s probably largely the latter, but “muscle memory” is still a convenient name.
However it works, and whatever you call it, I maintain that most of the time it is very handy. However, there are times when it can prove to be more of a hindrance.
Largely because I do quite a lot of typing in foreign languages that use diacritics (i.e. accent symbols), I regularly find myself having to reach for these characters. In the old days, I used to have to remember or look up the ASCII codes for the characters I wanted (fortunately, back then it was mostly acute and sometimes grave or circumflex accents on vowels, and perhaps the occasional cedilla, for typing in French).
Both my home and office PCs have somewhat more sophisticated methods set up for accessing special characters. Unfortunately they are slightly different, which is where the muscle memory can get in the way.
At home I use Linux most of the time, and I have a Compose key (currently the right “Windows” key, which isn’t used for anything else by default on Linux) set up on my keyboard. Pressing this key followed by a pair of other keys produces a character determined by the keys pressed (a so-called “compose key sequence”); e.g. “compose” + ‘a’ + ‘`’ (that’s a backtick, which hangs out just to the left of the number 1 on a UK keyboard, in case you were wondering) produces ‘à’. Many of the compose key sequences, such as this one, are fairly intuitive and easy to remember (or, you can just make an educated guess and if it doesn’t produce the expected result, delete it and try it again or look it up). This is a very straightforward way of making a lot of special characters available on a standard keyboard, and is my favourite solution to the problem.
At work, I use a Windows machine. On it I have installed a handy little utility called To Bach, which is actually designed to facilitate typing in Welsh but allows typing of the accents found in Welsh (mostly circumflex accents (â) – called to bach (“little roof”) in Welsh, hence the name of the software – and, less often, acute (á) and grave (à) accents on all the vowels – that’s a, e, i, o, u, y and w in Welsh – as well as a diaeresis (ä), which as far as can remember only occurs on the letter i in Welsh but can actually be typed on any vowel with To Bach) as well as certain other special characters such as ç and ñ that don’t actually appear at all in Welsh. It is set up by default to use the right Alt key as the main trigger key. For circumflex accents (the most common by far in Welsh), you just hold down that key (and Shift if you want a capital letter) and type the vowel you want. For the others, you hold down the trigger key and then hit another key (e.g. ‘\’ to get a grave accent) before letting go of both and hitting the vowel key for which you want the accent.
Both methods are very straightforward but because they are different I often find myself reaching for the wrong key combination (e.g. “right Win” + ‘a’ + ‘`’ instead of “right Alt” + ‘\’ + ‘a’ if I want an ‘à’ at work).
The obvious solution, which I may get round to at least partially implementing at some time, would be to reconfigure my Linux compose key settings to match To Bach (as I don’t think it’s possible to edit the configuration of the latter). Alternatively, there are Compose key utilities available for Windows, which would also give me easy access to characters that aren’t currently available via To Bach (e.g. if I want an ‘å’ on Windows – not that I often do – I currently have to either fire up the handy (but not quite so handy as To Bach/Compose) Character Map utility or remember the Alt+134 combination, while on Linux I just have to hit “compose” + ‘o’ + ‘a’) so I could just install one of those and drop To Bach, although having used it for quite a few years I’d be sad to stop using it now.