How to fix / refresh start menu in Windows 10? How to add / remove / edit items in bulk?

(Edit: This answer mostly relates to Windows 10 prior to Version 1511.)

The Windows 10 Start menu has several known bugs. You might have run against the particularly noxious bug limiting the total number of entries to 512. That's not 512 applications, by the way - that's 512 items in total, including apps, folders, files and shortcuts. (EDIT: starting with Version 1511 Microsoft has significantly increased this limit.)

The best solution, in my opinion, is not to fight against these bugs, since you really have no other option than wait for a fix from Microsoft. Instead, until Microsoft gets its act together, replace its Start menu with a third-party one. The top contenders are :

• The free Classic Shell (recommended)
• Start10 ($4.99)

Otherwise, here is a list of workarounds for the Microsoft one :

1. Rebuild the search index by going to Control Panel / Indexing Options / Advanced and using the Rebuild button.
2. Reset the Start menu layout by opening an elevated command prompt, exit Explorer, delete the Start menu database at %LocalAppData%\Microsoft\Windows\appsFolder.menu.itemdata-ms and run Explorer again. (EDIT: this file no longer exists in newer versions of Windows 10.)
3. Ensure your Windows 10 Start Menu does not exceed 512 items by reducing the number of indexed locations
4. Reinstall all applications, by entering in Powershell as Administrator
   Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
5. Try a new user account, since your profile might be damaged

Even if one of the workarounds works for you, the bug can hit again at any time. The only lasting solution is to use a more stable Start menu replacement.

To "refresh" the Start Menu, follow these steps:

1. Open the "Run command" window by pressing WIN+R.
   (i.e. hold down the Windows key and then press R.)
2. Type "cmd" at the prompt, and press Enter.
3. Wait for the command prompt to open.
   (It will be a flashing cursor block.)
4. At the command prompt, type this:
   taskkill /IM explorer.exe /F
   You should notice these all vanish: Start Menu, Taskbar, any open File Explorer windows.
5. Type this at the command prompt:
   explorer.exe
   Now those components should all load back in.
6. Close the command prompt and try the Start Menu. Hopefully it should have refreshed.