I know for sure Korean does this, though technically their writing system is a syllabary. Symbols representing vowel and consonants are arranged into blocks that represent a syllable.

For example ㅈㅅ is short for 죄송합니다 meaning “I’m sorry”. Talk about efficient shorthand! The first consonants of each syllable block are used to makeup the shorthand, the ending 합니다 is a polite conjugation which is ignored in shorthand. You can look up “korean texting slang” for more. It’s apparently used a lot. The shorthand some might already be familiar with is ㅋㅋ which is “lol”.