The best replacement for notability is notes plus.

The best alternatives to notability are rated as following:
★★★★★  notes plus
★★★★  goodreader
★★★★  goodnotes
★★★  iannotate
★★★  onenote
★★★  penultimate
★★★  notetaker hd
★★★  evernote
★★  goodnotes 4
★★  note anytime
★★  noteshelf
★  note taker hd
★  supernote
★  livescribe
★  bamboo paper
★  awesome note
  remarks
  pdf expert
  note taker
  note shelf

Your alternative for notability is not listed? Suggest!
Speaking about notability, one probably shouldn't forget about jot script.

Other search terms related to notability and their ratings are:
★★★★★ jot script
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notability
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