If a picture with Greek characters or other symbols from the Symbol font is opened in Metafile Companion, all the Symbol font characters turn into question marks (e.g. “????”). If the file is then saved, the Greek characters or other symbols are saved as question marks (and will appear as question marks if the picture is inserted into another document).
Metafile Companion appears to not be handling the character set for this special Symbol font correctly when opening the file.
If a new picture is created in Metafile Companion (or if an existing picture is edited) and new Greek characters are added (or you re-edit the text with the question marks), and then the file is saved, the file will contain the proper Symbol font characters (and will appear as Symbol font characters if the picture is inserted into another document). You just can’t re-edit the metafile (or if you do, you’ll need to re-add (or re-edit) the Greek characters). So the basic rule here is “If you see Greek characters on screen, they will be saved as Greek characters. If you see question marks, they will be saved as question marks.”
Another work-around is to use the metafile editor built into some other software to edit the Greek characters. For example, in Microsoft Word, right-click the inserted picture and choose the “Edit Picture” command.
Finally, Metafile Companion v1.3 added support for the Unicode character set (that includes characters from every language). So upgrading to the latest version may allow you to paste special text with characters outside of the ANSI and ASCII character sets.