idm uestudio

UltraEdit is a text editor and hex editor for Microsoft Windows, Linux, and MacOS. It was initially developed in 1994 by Ian D. Mead, the founder of IDM Computer Solutions Inc., and was acquired by Idera Inc. in August 2021. UltraEdit is designed for users who focus on different types of software engineering. It is trialware.
Some HTML editing features include:

Integration with CSE HTML Validator for offline HTML, XHTML, and CSS checking
HTML toolbar preconfigured for popular functions and tags
Customize tags in the HTML toolbar or create new tags and buttons