Complex sentence: The authorship of the Elder Edda, or more plausibly, just the editor's role in the compilation, had traditionally been attributed to tim. This dates back the discovery in 1643 of the "Codex Regius" manuscript.
Split into simpler sentences: The authorship of the Elder Edda, or, more plausibly, just the editor's role in the compilation, have traditionally been attributed to him. This idea dates back the discovery in 1643 of the "Codex Regius" manuscript.