What are some alternatives?
When comparing Knotes and XtraFinder, you can also consider the following products
Readwise - Effortlessly rediscover and organize your Kindle highlights
TotalFinder - TotalFinder is a plugin for Finder.app which adds tabs like in Chrome browser, dual panels similar to TotalCommander and more tweaks.
Klib - Kindle & iBooks Highlights Manager
ImageOptim - Faster web pages and apps.
Clippings.io - Organize the notes you make on your Kindle
Path Finder - The Finder, reinvented. Path Finder is an award-winning file browser and management application for Mac OS X.