Based on @FranBurstall, I looked at the documentation, and then I wrote the following:

;; Define a function to enable markdown-mode after Emacs Anywhere is invoked (defun pmd/markdown-mode-emacs-anywhere (app-name window-title x y w h) (markdown-mode)) ;; Hook your function (add-hook 'ea-popup-hook 'pmd/markdown-mode-emacs-anywhere) 

Not sure if this is the most elegant way to do it... But it works! :)

Based on @FranBurstall, I looked at the documentation, and then I wrote the following:

;; Define a function to enable markdown-mode after Emacs Anywhere is invoked (defun pmd/markdown-mode-emacs-anywhere (app-name window-title x y w h) (markdown-mode)) ;; Hook your function (add-hook 'ea-popup-hook 'pmd/markdown-mode-emacs-anywhere) 

Not sure if this is the most elegant way to do it... But it works! :)

I tried removing all parameters. But it broke the function. So I am leaving it with all this unused parameters.