The combining dot above is sometimes used instead of combining stroke above over vowel signs. I would say that it is not part of the primary set in the sense that it simply a scribal alternate of the combining stroke above, but some scholars insist on making a difference (I am not one of those).
All letters except 2c93 and 2cdd can take a macron
Only 2c93 can take a diairesis
2c81, 2c89, 2c93, 2c9f, 2ca5, 2ca9, 2cb1 can take a dot (instead of macron, or in case of 2c93, instead of diairesis)
btw those notes hold for onw
for fia, dgl, xnz: