Export the JSON and upload it

One charter party: on its page press e-Charter party JSON. Unsaved changes are saved first.

Several at once: Charter parties in the menu → tick them → e-Charter party JSON. You get one file with all of them.

Then on echarterparty.yna.gov.gr use the bulk upload and choose the file.

The file follows the platform's format: texts in Latin capitals, nationalities as ISO 3-letter codes (GRC, DEU…), times in UTC, empty fields left out, the booking reference as client_id so errors on the platform point to your booking. Exported charter parties show Exported with the date.