Existing EU language guidelines
EU Interinstitutional Style Guide
The Publications Office of the EU has released instructions on gender-neutral language in its style guide. The focus is on gender-neutral drafting of texts and it includes useful writing tips. It is currently only available in English language.
English Style Guide by the Directorate - General for Translation
The English style guide is a handbook for authors and translators in the European Commission and includes a section on gender-neutral language. It includes the same guidelines as the EU Inter-institutional style guide.
Fundamental Rights Agency (FRA) Style Guide for Authors
The style guide includes a section on avoiding discriminatory and offensive language and using gender-neutral language.
Source: Style guide for authors