SciTE is a powerful programmer's editor and Notepad replacement based on the popular open-source Scintilla (a component used within many other editing tools).
You don't need to be a developer to use the program. It looks much like Notepad, so at a minimum you can just launch it, type some text and save the file, using all the keyboard shortcuts you know already.
It won't take long to notice small benefits. Pressing Ctrl+N creates a new tab, for instance, allowing multiple documents to be open at once. And Ctrl+F gives you a persistent search area at the bottom of the screen, where you can instantly mark all search hits as well as zip through them one-by-one.
Start exploring the program and you'll quickly discover more. Regular expression searches, find across files, drag and drop editing (select some lines, drag and drop them somewhere else), case conversion, bookmarking, session management.
There's also plenty of developer-oriented power, including syntax highlighting, brace handling, code folding, and options to compile and run programs, turning it more into a basic IDE.
Version 3.7.3 Changelog
Display block caret over the character at the end of a selection to be similar to other editors.
In SciTE can choose colours for fold markers. Feature #1172.
In SciTE can hide buffer numbers in tabs. Feature #1173.
The Diff lexer recognizes deleted lines that start with "--- ".
The Lua lexer requires the first line to start with "#!" to be treated as a shebang comment, not just "#". Bug #1900.
The Matlab lexer requires block comment start and end to be alone on a line. Bug #1902.
The Python lexer supports f-strings with new styles, allows Unicode identifiers, and no longer allows @1 to be a decorator. Bug #1848.
Fix folding inconsistency when fold header added above a folded part. Avoid unnecessary unfolding when a deletion does not include a line end. Bug #1896.
Fix finalization crash on Cocoa. Bug #1909.
SciTE on GTK+ can have a wide divider between the panes with the split.wide property.
Fix display of autocompletion lists and calltips on GTK+ 3.22 on Wayland. Newer APIs used on GTK+ 3.22 as older APIs were deprecated.
Fix crash in accessibility code on GTK+ due to signal receipt after destruction. Bug #1907.
Make trackpad scrolling work on Wayland. Bug #1901.