Add "Open with Sublime Text 3" to Windows Explorer Context Menu (including folders)

OpenWithSublimeText3.bat

@echo off
SET st2Path=C:\Program Files\Sublime Text 3\sublime_text.exe
 
rem add it for all file types
@reg add "HKEY_CLASSES_ROOT\*\shell\Open with Sublime Text 3"         /t REG_SZ /v "" /d "Open with Sublime Text 3"   /f
@reg add "HKEY_CLASSES_ROOT\*\shell\Open with Sublime Text 3"         /t REG_EXPAND_SZ /v "Icon" /d "%st2Path%,0" /f
@reg add "HKEY_CLASSES_ROOT\*\shell\Open with Sublime Text 3\command" /t REG_SZ /v "" /d "%st2Path% \"%%1\"" /f
 
rem add it for folders
@reg add "HKEY_CLASSES_ROOT\Folder\shell\Open with Sublime Text 3"         /t REG_SZ /v "" /d "Open with Sublime Text 3"   /f
@reg add "HKEY_CLASSES_ROOT\Folder\shell\Open with Sublime Text 3"         /t REG_EXPAND_SZ /v "Icon" /d "%st2Path%,0" /f
@reg add "HKEY_CLASSES_ROOT\Folder\shell\Open with Sublime Text 3\command" /t REG_SZ /v "" /d "%st2Path% \"%%1\"" /f
pause

Worked like a charm :)

Add these lines to open directory when right-clicking inside it

rem add it for folders when inside them
@reg add "HKEY_CLASSES_ROOT\Directory\Background\shell\Open with Sublime Text"         /t REG_SZ /v "" /d "Open with Sublime Text"   /f
@reg add "HKEY_CLASSES_ROOT\Directory\Background\shell\Open with Sublime Text"         /t REG_EXPAND_SZ /v "Icon" /d "%st2Path%,0" /f
@reg add "HKEY_CLASSES_ROOT\Directory\Background\shell\Open with Sublime Text\command" /t REG_SZ /v "" /d "%st2Path% \"%%W\"" /f

I had to replace all instances of "Sublime Text 3" with "Sublime Text".

Also, you can also remove the entries with this.

I have summarized everything from above for the sake of simplicity in a script and adapted it for Sublime Text 4. Just save it as .bat and run it as administrator:

@echo off
SET stPath=C:\Program Files\Sublime Text\sublime_text.exe

rem add it for all file types
@reg add "HKEY_CLASSES_ROOT\*\shell\Open with Sublime Text"         /t REG_SZ /v "" /d "Open with Sublime Text"   /f
@reg add "HKEY_CLASSES_ROOT\*\shell\Open with Sublime Text"         /t REG_EXPAND_SZ /v "Icon" /d "%stPath%,0" /f
@reg add "HKEY_CLASSES_ROOT\*\shell\Open with Sublime Text\command" /t REG_SZ /v "" /d "%stPath% \"%%1\"" /f

rem add it for folders
@reg add "HKEY_CLASSES_ROOT\Folder\shell\Open with Sublime Text"         /t REG_SZ /v "" /d "Open with Sublime Text"   /f
@reg add "HKEY_CLASSES_ROOT\Folder\shell\Open with Sublime Text"         /t REG_EXPAND_SZ /v "Icon" /d "%stPath%,0" /f
@reg add "HKEY_CLASSES_ROOT\Folder\shell\Open with Sublime Text\command" /t REG_SZ /v "" /d "%stPath% \"%%1\"" /f

rem add it for right-clicking inside folders
@reg add "HKEY_CLASSES_ROOT\Directory\Background\shell\Open with Sublime Text"         /t REG_SZ /v "" /d "Open with Sublime Text"   /f
@reg add "HKEY_CLASSES_ROOT\Directory\Background\shell\Open with Sublime Text"         /t REG_EXPAND_SZ /v "Icon" /d "%stPath%,0" /f
@reg add "HKEY_CLASSES_ROOT\Directory\Background\shell\Open with Sublime Text\command" /t REG_SZ /v "" /d "%stPath% \"%%W\"" /f
pause

I just don't understand why a $100 application doesn't have something as essential as this..

Thanks, @KasimirRomer. It works in Build 4126

You can use
HKEY_USERS\{the-account-SID}\Software\Classes
instead of
HKEY_CLASSES_ROOT

That way you don't need admin rights.