Dot accent used in Polish and other languages look here

Tim

Dot accent is a quite common diacritical mark in some European languages. It is used in Maltese (over ‘c’, ‘g’, ‘z’), Lithuanian (over ‘e’), Polish (over ‘z’) and Turkish (they distinct between i/İ — ı/I — i with and without dot). And actually, the dot as a diacritical mark can be found in every language using Latin script over ‘i’.
More at Project Diacritics

Spooky, just last week I was thinking that in German one could get away with making the umlaut one dot… It would be especially helpful in caps. If you did this at the type design level, the font would not be [easily] usable for a language that uses both single and double dots [on the same vowels]. Are there any such languages Filip? While if you did this at the composition level, you’d have to worry about circumventing spell-checking issues.

Or what about using a macron-style umlaut?

hhp

Catalan (u/c & l/c I and U for diaeresis and u/c & l/c L for dot) and Turkish (u/c & l/c O and U for diaeresis and u/c I for dot) use both but not on the same character and Hungarian uses the diaeresis (umlaut) and double acute (Hungarian umlaut). Macron seems to be Lithuanian and Latvian also used for transliteration of Arabic.
Tim