Hello tsoukalasdesign, welcome to the forum.
Hello,
There are two possibilities for your wish:
- the (Greek) operating system supports the composition of ‘A’ into a glyph.
- you can create 'A as a so-called ligature. In Fontself, the symbol must then end with .liga in the Layers window, i.e. 'A.liga
As an example, you can have a look at my character for 40 Latin languages: Free font TimeSaver - #9 by urs7000