dumb newbie question

I am trying to edit some code in the Arduino IDE.
The edit screen is darkened and I can read the code and move the cursor around with the arrow keys.
But I can not edit the code. How to edit in the Arduino IDE? Maybe there is some setting I have forgotten about.
It was editing two months ago, but don't remember how I did it :blush:.

Thank you for your help.

Here is what the darkened screen looks like:

Found the fix:
File > Preferences > uncheck: Use External Editor

(I had "External Editor" checked for editing in Vim)