YES. It is possible to send multiple registrations in a system-to-system modality or by manual upload of models in a file.
System-to-system means a computer in the supplier premises sends a ZIP file containing an XML with multiple records with models structured data (and all the necessary attachments, like labels or technical documentation). EPREL system will receive this ZIP file, it will extract the content and it will register the models in the database from the records in the XML file and uploading the attachments in the server.
Manual upload of models in a file will do the same thing as system-to-system but the difference is that the ZIP file will not be send by a computer and received by EPREL computer, it will be uploaded manually using the UI by a person working at the supplier.
If models are declared equivalent to a base model, then all the mandatory data for the base model has to be entered first. The equivalent models will include the EPREL registration number of the base model they are declared as equivalent to.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.