Probably is across all the Google apps.
I dunno if this will work in sheets, but in Word the way to insert a gap or space into a word where there wasn't a space was to draw a line downwards at the point you want the space
So ThrobbingAngel would become Throbbing Angel if you inserted a down stroke between the g and A like this Throbbing
Angel.
It might be to do with you working in Sheets, though - number based innit. When using Word or Docs the system seemed to just insert spaces as needed. I think you naturally leave one as if you were writing on paper and the handwriting 'engine' is somewhat intelligent so would recognise Throbbing as a word and expect a space, comma or full stop after it.
Try Docs