Mac storage basics · Checking your storage
Where did the Storage tab in About This Mac go?
Short answer: From macOS Ventura onwards it lives in System Settings → General → Storage. About This Mac's More Info button takes you to the General settings, where Storage is listed.
Since macOS Ventura (13), storage moved out of About This Mac into System Settings → General → Storage. About This Mac now shows a short summary; its More Info… button opens the General settings, where Storage is one of the rows.
Everything the old Manage… button offered is still there: the category breakdown, the recommendations (Store in iCloud, Optimise Storage, Empty Trash Automatically) and the info buttons that let you review large files and per-category items.
If you want a deeper, folder-level view than macOS gives, Storage Studio's What's Using Space lists your largest folders and lets you drill into any of them. See the Storage Inspector.