230c3a4に基づく．さらにあちこちかけるようにした．そして指定方法を少し変更した．top-leftとかとyokoとかの指定を逆にした．こんな感じ：

\jlreqtrimmarkssetup{
  banner_font = {\small},
  banner = {
    top-left = {
      yoko = {odd = {奇左上横}, even = {偶左上横}},
      tate = {odd = {奇左上縦}, even = {偶左上縦}},
      corner = {odd = {[odd]\thepage}, even = {[even]\thepage}},
      in-yoko = {odd = {奇左上内横}, even = {偶左上内横}},
      in-tate = {odd = {奇左上内縦}, even = {偶左上内縦}},
    },
    top-right = {
      yoko = {odd = {奇右上横}, even = {偶右上横}},
      tate = {odd = {奇右上縦}, even = {偶右上縦}},
      corner = {odd = {奇右上角}, even = {偶右上角}},
      in-yoko = {odd = {奇右上内横}, even = {偶右上内横}},
      in-tate = {odd = {奇右上内縦}, even = {偶右上内縦}},
    },
    bottom-left = {
      yoko = {odd = {奇左下横}, even = {偶左下横}},
      tate = {odd = {奇左下縦}, even = {偶左下縦}},
      corner = {odd = {奇左下角}, even = {偶左下角}},
      in-yoko = {odd = {偶左下内横}, even = {偶左下内横}},
      in-tate = {odd = {奇左下内縦}, even = {偶左下内縦}},
    },
    bottom-right = {
      yoko = {odd = {奇右下横}, even = {偶右下横}},
      tate = {odd = {奇右下縦}, even = {偶右下縦}},
      corner = {odd = {奇右下角}, even = {偶右下角}},
      in-yoko = {odd = {奇右下内横}, even = {偶右下内横}},
      in-tate = {odd = {奇右下内縦}, even = {偶右下内縦}},
    },
    top-center = {
      left = {odd = {奇上中央左}, even = {偶上中央左}},
      right = {odd = {奇上中央右}, even = {偶上中央右}},
      in = {odd = {奇上中央内}, even = {偶上中央内}},
    },
    bottom-center = {
      left = {odd = {奇下中央左}, even = {偶下中央左}},
      right = {odd = {奇下中央右}, even = {偶下中央右}},
      in = {odd = {奇下中央内}, odd = {偶下中央内}},
    },
    center-left = {
      above = {odd = {奇左中央上}, even = {偶左中央上}},
      below = {odd = {奇左中央下}, even = {偶左中央下}},
      in = {odd = {奇左中央内}, odd = {偶左中央内}},
    },
    center-right = {
      above = {odd = {奇右中央上}, even = {偶右中央上}},
      below = {odd = {奇右中央下}, even = {偶右中央下}},
      in = {odd = {奇右中央内}, odd = {偶右中央内}},
    },
  }
}

inがついているキーは仕上がり版面内．キーが省略された時のデフォルトは，top-left，yoko．odd / evenに対しては偶奇共用の設定になる．

さすがにやり過ぎだろうか……．