How to make the console of the Firefox DevTools multi-line? I am aware of the Shift+Enter keyboard shortcut, which makes the command line go to the next line. Though like in Firebug, I want to vertically separate my console into command line and results part, but I can not find that functionality.
You can try the scratchpad. Go to Settings >> Available Toolbox Buttons and check the box for scratchpad. Refer the screenshot:
Once done, you'll have a notepad-like icon in your developer console navigation bar on the right side...
. Click on it and it will open a scratch pad on which you can write code and execute...
Good Luck.
The command line the Firefox DevTools has a "smart multi-line" feature. That means it detects when a command is not finished and automatically inserts a line break, e.g. when you write document. and hit Enter. As you mentioned, you can also insert a line break manually by pressing Shift+Enter.
The DevTools also offer a completely separate command editor panel called Scratchpad, which you can enable via the settings (under the Default Developer Tools* section).
There is currently no multi-line editor as a side panel like Firebug's Command Editor, but it is already requested.
This is also described in the migration guide for Firebug users.
来源：https://stackoverflow.com/questions/41948364/how-to-activate-multi-line-command-line-in-firefox-devtools