As a rule of thumb the ESEF taxonomy contains all elements present in the IFRS taxonomy, regardless of their endorsement status with the IFRSs in the EU.
However, elements which correspond to IFRSs not endorsed by the EU (but considered the equivalent to IFRS based on the Commission Decision 2008/961/EC) are provided with the sole purpose of facilitating compliance with the ESEF regulation for third country issuers listed on EU markets.
European issuers must under no circumstances use taxonomy elements not endorsed by the EU when tagging their consolidated financial statement. Failing to adhere to this is a breach of the requirement contained in Annex IV.3 of the RTS on ESEF.
How to use elements available in the IFRS Taxonomy which are not yet available in the ESEF Taxonomy
If you determine that the IFRS Taxonomy includes an element which corresponds to a disclosure in your IFRS financial statements (and that this element isn't yet included in the ESEF taxonomy) you should define an extension with a name and label corresponding to the name and label of the element in the IFRS taxonomy.
When the new element is then included in the core ESEF taxonomy, you should adopt use of the new ESEF taxonomy element in both the current reporting period and when tagging comparative figures from previous reporting periods in your current report.