Many people don't know this, but you can open a navigator window in REAPER to explore your projects like this 🔻
You can find this in the View menu → Navigator.
You can also find it in the Actions menu and set a shortcut for it. It’s called “View: Show navigator window” and I have it set to ctrl/cmd + shift + v.
And if you wanna dock it, just right click and select "Dock navigator window in docker" this way you can place it anywhere in your screen.
I’ve seen a lot of people leave this always docked on top of their ruler and it’s super nice!
I hope this thing helps you browse your big project easily! 💙