IndentByFold is an auto indent plug-in for Notepad++ based on the language folding points.
To download version 0.7.3 (2019-11-10) go to the release page.
The source code of IndentByFold can be found at GitHub.
The easiest way to install is to download it through the Plugins Admin in Notepad++.
To manually install the plug-in, copy IndentByFold.dll to the plugins\IndentByFold directory. Then (re)start Notepad++.
The documentation of IndentByFold can be found at Read the Docs. This includes: