KJots is described as 'hierarchical note taking application that organizes all of your notes into separate books displayed as tree. Since Plasma 5 KJots isn't part of Kontact anymore' and is an app in the Office & Productivity category. There are more than 100 alternatives to KJots for a variety of platforms, including Windows, Mac, Android, Linux and Online / Web-based. The best alternative is Joplin. It's not free, so if you're looking for a free alternative, you could try Standard Notes or Microsoft OneNote. Other great apps like KJots are Evernote (Freemium), Simplenote (Free, Open Source), CherryTree (Free, Open Source) and Zim (Free, Open Source).
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.