Is ONE PIECE episode 735 filler?
Canon No, episode 735 of ONE PIECE is canon.
#735
The Unheard-of! Admiral Fujitora's Surprising Decision!
前代未聞 大将藤虎衝撃の決断！
Aired 3 Apr 2016
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.