I don't sing the praises of readwise.io nearly often enough. All my notes and highlights end up there for future reinforcement, whether from papers (Zotero), the interweb (Raindrop), books (Kindle), etc. They also all flow back to Obsidian, my notetaking app, so they are linkable and searchable there. No longer having islands of notes, or books on which I have taken notes but forgotten about them, has long such a mundanely important advance for me.