add custom word boundary for japanese (hanzi based languages too maybe?)

Perhaps all of these problems will go away with improved japanese parsing, but it would be nice if I could custom define a word which gets added to the vocabulary list (or really, just custom define it’s boundary). For example:

スゲえ… is currently split into スゲ (sedge) and え (huh) instead of the correct incredible/unbelievable as is provided by yomichan (with jmdict) so if the word boundaries could be manually selected, that would be useful since I assume even with parsing improvements, it likely still won’t be perfect.