Wystąpienie pierwsze w sesji drugiej

Practically speaking: each item on the agenda = one abstract entry. Group „Tuesday/Wednesday” by day taxonomy (or by programme date). Sections „SESSION I…VII” are grouped by session. The column „Danka Auditorium / room 347…” is grouped by room.

„Time” with programme-start + programme-end. „Duration” with programme-duration. You can keep „Moderator” at the session level as a field in session positions (or in the future as a separate „session” type, but here we stick to your condition: expand the existing type and maintain backward compatibility).