Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Stickies Capture by Miro - Digitize and edit handwritten sticky notes
Create Issue Branch - Automates the creation of issue branches on GitHub
Thought Train - Stop using sticky notes to remember what you're doing 📒 🚫
REVISR - Git Management for WordPress : keep track w/ version control
PotatoNotes - POSP official notes app, will be included sometime idk