Kate

Kate, the big sister of text editing applications

Kate has all the features of KWrite, and much more. It is a multi-document or multi-view editor, which means that you can have several documents open at the same time, or you can have several views of the same document.

Document modification monitoring gives you ample warning of danger.

Kate's many features include

Multi-Document Interface
Window tabbing and window splitting
Character encoding support and conversion
Syntax highlighting and bracket matching
Code and text folding
Auto-indentation
Auto-completing
Block selection
Regular Expression find and replace
Scriptable using JavaScript

and much more

Visit the project pages for more information