Is there any character like that?

[nablator]

Red: Middle Ages, blue: modern times. This change took place around 1400.

True, but more progressively: spellings were updated very slowly during the 15th century and even later during the 16th century you could still find many medieval spellings in books. The most common changes being e -> ae/oe and ci -> ti, others like mpn -> mn were much less frequent.

It's possible but unusual to find both spellings of the same Latin word in the same book: spelling was a lot more consistent in Latin than in (most?) vernacular languages.

Two reasons why the statistical impact of these changes was negligible as early as the 1420s-1430s in most Latin manuscripts.