This is how I use NeoVim's terminal: run a command, visually select the lines I want to operate on and yank them, then paste them in a new buffer. After that, it's a matter of transforming the text via whatever means one normally does (macros, text objects, search/replace, etc.)
Manipulating text within the editor is pretty common; e.g. I use shell-mode in Emacs, which is mostly just a normal text buffer (except Return acts differently when the cursor is over the commandline!); eshell is similar.
What I was describing above is manipulating such buffers with external commands (similar to Emacs `shell-command-on-region`)
