Looking for Notepad++ alternative for Rich Text Format

I’m looking for simple and lightweight text editor (or rather word processor) for MS Windows like Notepad++ but that allows to bold, underline and highlight section of text (like style tokens in np++) and save file that when you reopen it later, the highlight would be still present. I know there is LibreOffice Writer but its way too advanced, heavy and slow. Dark (night) mode or customizable styles, tabs support and search form would be awesome.

Are there any such a free software (preferably open-source)?