In EmEditor you can do such things by utilizing external command-line tools,
for an HTML Tidy example see e.g. https://www.emeditor.com/forums/topic/xml-without-line-breaks/
Tidy reads HTML, XHTML and XML files and writes cleaned up markup.
Also you can g00gle e.g. for “Artistic Style” (http://astyle.sourceforge.net/)
A Free, Fast, and Small Automatic Formatter for C, C++, C++/CLI, Objective‑C, C#, and Java Source Code
There are many of them.
Or search here the Library if there is a script already.
If you need help on Tool setup, just ask.