@peemee I thought I’d try your text replacement idea but I noticed two things: A) it only works for a whole word with a preceding space, so you can’t use it to append a word ending, and B) it refuses to input the single straight speech mark* even though the shortcut is set up that way. It always reverts to ‘. All other alternatives characters seem to work, just not that one. It’s strange. I’m on iOS 12.4.
*Well, it may be an apostrophe rather than a speech mark.