Whether you just closed a tab accidentally or have one in the back of your mind you need back, Command + Shift + T can get it back. Press it once to reopen your last closed tab, and keep pressing it ...
Deleting the WinSxS folder is unsafe. Learn what WinSxS does and how to clean it safely using Disk Cleanup, Storage Sense, and DISM to free real space in Windows 10 and 11.