Knotable is described as 'Pull everything together -- people, notes, tasks, dates, files, links, all of it' and is an app in the Social & Communications category. There are more than 50 alternatives to Knotable for a variety of platforms, including Windows, Android, Mac, iPhone and Online / Web-based. The best alternative is Joplin, which is both free and Open Source. Other great apps like Knotable are Standard Notes (Freemium, Open Source), Google Keep (Free), Microsoft OneNote (Freemium) and Evernote (Freemium).
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.