Are there rules for "pronunciation" 略字?


I get that this might be subjective since 略字 themselves originated (mostly)
subjectively, but are there any rules for being able to create/use new ones?
For example, the [广+マ](https://japanese.stackexchange.com/q/78677/78)
representing 魔 or 摩 is quite common. [This blog
post](https://soranews24.com/2017/02/02/w-t-f-japan-top-5-most-ridiculous-
kanji-handwriting-shortcuts%E3%80%90weird-top-five%E3%80%91/) shows 木 + ｷ to
represent 機 (which I've seen), but it also shows 艹+ヤ for 薬 (which I hadn't
seen).

So can you just make up and use something that would be easily recognizable?
Like the other night I was having trouble remembering the stroke order for 華.
I thought, "Could I just write 艹+カ for 華・花? And would people understand it?"




Something like "木+キ" is an outdated convention used before 1970 when no one
had a computer (the tweet clearly says how retro it looks). "广+マ" and
"simplified 門" are still sometimes seen in manga, but I feel even these have
started to look a bit old-fashioned now. As for others, you should not use
them unless you are making an early-Showa film or something. It is not
recommended to create such abbreviations simply because some kanji are hard to
remember. If you use "艹+カ", young readers probably can't even understand what
you are trying to do. In most cases, you should [simply use
kana](https://japanese.stackexchange.com/q/19491/5010) (or if you're feeling
adventurous, [invent a KY語](https://japanese.stackexchange.com/a/69906/5010)).

