In Polish language the eight standard letters have also the diacritical variant.
To type these diacritical letters on the screen, the right Alt key should pressed prior to the desired letter. But in the "Title edition" mode of Pinnacle 26, two diacritical letters "c" and "o" are not available in this way.
In case of "c" the "Control panel" window opens, and in case of "o" where is no effect. But everything is OK during the "Project note" edition.
So the only way to get the diacritical "c" and "o" in "Title edition" mode is to copy them from "Project note" (or other text edior) and paste to "Title edition".
And all users of Pinnacle 26 whom I know have the same problem, so it must be the manufacturing defect.