Hi All, This problem appears when a combination of ARCHICAD localization settings, OS's language settings and Font Type is not correctly set.
Please set the 'Preferred Language' in 'System Preferences' to Greek (or other preferred language) on MAC OSX and use Fonts which support it's characters. Otherwise there will be "?"(question mark) signs in some parts of the program. The real solution to this kind of problem will appear in AC21.
In the meantime, please see the attached image on how to set Greek language eg. for Mac (for the Windows platform there is already a solution showed below to set the right Font Script Code). With the right setting, the problem with the "?" signs will be gone both for tabs and Schedules. Best, k