Notepad++ is a powerful text editor that implements some basic tagging and formatting that gives it some limited IDE Functionality. It is equipped with many languages by default and can format their text automatically based on the file extension. It also allows you to create your own User Defined Languages (UDLs) to format other filetypes in a custom manner. This page includes two UDLs for viewing MIB files in NotePad++, both UDLs are identical in function but one has the colors modified for better viewing for those who prefer Notepad++'s 'darkmode' view.
.\AppData\Roaming\Notepad++\userDefineLangs
Languages -> User Defined Languages -> Open User Defined Language Folder
Languages -> MIB/MIB (Dark Mode)
For more information please reference: Notepad++ User Manual on UDLs
User Defined Languages Light Mode and DarkMode
userDefineLang-MIB.xml userDefineLang-MIB-DM.xml