And for editing that command line... I know a lot of people who know about Ctrl-a, Ctrl-e, Ctrl-k, but still hold down the left arrow key or delete key a lot to edit things in the middle.

Those people want to use:

    Alt-f    move cursor forward one word
    Alt-b    move cursor back one word
    Alt-d    delete to the end of the next word
    Alt-Del  delete backwards to the start of the previous word

    Ctrl-_   undo

Here's a cheatsheet: https://readline.kablamo.org/emacs.html