This is the right place to continue this discussion: https://www.openstreetmap.org/changeset/144910854

Hallo Vanja!

Thank you for your answer! As far as I know it is possible to use both Latin and Cyrillic letters in Serbia, isn't it? Using tag "int_name" would be a possible compromise. But also the using of the tag "nat_name" for the Cyrillic letters would be possible.
Please read also https://wiki.openstreetmap.org/wiki/Relation:superroute, including the example. The addition of “E4” would be important to indicate that it belongs to the corresponding “superroute”. 

With friendly greetings
Stadtigel from Germany