From The K Language Wiki

The following editors/editor plugins add syntax highlighting and support for K:

Editor Features
q-mode Emacs K and q syntax highlighting, debugging tools, interaction with executable
ngnk-mode.el Emacs mode for using ngn/k & repl features
ngn/k/vim-k Vim K syntax highlighting, file detection.
vscode-q VS Code Syntax highlighting, language server, query visualization
ktye/kdb kdb (browser) K debugger with breakpoints, online
language-kdb-q Atom q/kdb+ language support
q-intellij-plugin JetBrains IDEs Syntax highlighting, code completion, declaration finding, code folding
k-akoune Kakoune Kakoune syntax highlighting and commands for K
sublime-q Sublime Text q/kdb+ syntax highlighting, server connection, plotting support, custom routines
jupyterq Jupyter Notebook K and q syntax highlighting, code completion, code help, inline charts and plots
ngn/k kernel Jupyter Notebook ngn/k support for jupyter kernel
oK mobile oK mobile (browser) Online graphing, plotting functionality, oK code execution, keyboard
kdbp-mode Emacs -
dqweb DQWeb (browser) Online interface for K processes with editing, syntax highlighting, autosave, persistence
Special K mode Codemirror Special K(K subset) syntax highlighting
k.esy EmEditor Syntax Highlighting
k.syn Vedit Syntax Highlighting
suhr/k-vscode VS Code