According to the 2018 StackOverflow Developer Survey, the popularity of development environments (IDEs, Text Editors) among software developers shows the following ranking:
Of these, only Vim, (DVT) Eclipse, and Emacs support editing in e-language (at least, last time I checked). Kate, which comes with KDE and also has a Specman mode, is not on this list.
I started using Sublime Text 3 some time ago. It offers packages that support a number of programming languages.
Though there is an e-language syntax available from Tsvi Mostovicz, it is unfinished work, and there are many syntactic constructs are missing. So, I created a fork of his project and finished it (it will eventually be merged back here).
It is a never-ending task because my code base for testing is limited and e is still undergoing development. The project is available through ST3's Package Control and you can contribute to it via Github.
I am eagerly waiting for your pull requests and/or comments and contributions!