Under the international standards of the European Digital COVID Certificate (EU DCC), vaccines adapted to a new variant are not differentiated on the COVID certificate. The distinction whether a vaccine is bivalent or monovalent is therefore not relevant for travel.
Note: The site that administered the vaccine to you must document bivalent vaccination in its primary system correctly and on a differentiated basis. At most vaccination centres you will receive printed proof of vaccination or an entry on your vaccination card from the medical professional after the vaccination. The proof document contains the place and date of the vaccination as well as information on the vaccine administered (trade name, manufacturer and lot number). It will show that you were vaccinated with the bivalent vaccine.
To learn how a bivalent vaccine differs from a monovalent one, see the FAQ «What is the difference between the previous mRNA vaccines and the variant-adapted ones?».