Maybe not Hammer Editor but still... I'm currently implementing a bit of Hammer into GMod, it will allow users to preview and edit entities. I think it will be a great tool
How to Optimize a Map in Hammer Editor: 10 Steps (with Pictures)
Opening Official Maps in Hammer [Counter-Strike: Global Offensive] [Tutorials]
How to install the Hammer Editor on Linux | TF2Maps.net
Valve Hammer Editor | Half-Life Wiki | Fandom
Level Design Introduction/Getting Started (Portal 2) - Valve Developer Community
Valve Hammer Editor - Combine OverWiki, the original Half-Life wiki and Portal wiki
VHE] Valve Hammer Editor Video Tutorials file - Goldsource Data Base mod for Half-Life - Mod DB
How to Optimize a Map in Hammer Editor: 10 Steps (with Pictures)
Valve Hammer Editor - Valve Developer Community
Screenshot of the Hammer editor | Download Scientific Diagram
Valve Hammer Editor - Official TF2 Wiki | Official Team Fortress Wiki