What does a red mark mean?

[ratijas]

What is this scary red mark on the left of a directory? How to revert it back to normal?

[CatsDeservePets]

It means you pressed d (as in delete/cut). It cuts the selected file into lf's clipboard. If you now navigate somewhere else, you can press p to paste the file into the current location.
There is also y (as in yank/copy) which copies the selected file into lf's clipboard. When pressing p, it creates a copy of the selected file in the current location und leaves the original file in place.

d -> Think of it as CTRL-X.
y -> Think of it as CTRL-C.

To clear the clipboard, press c for clear. Clearing does not touch your existing files in any way.

See also our documentation.

[ratijas]

OMG, thank you for saving my folder!

Any other potentially destructive keys that I should be aware of? For a single-key action (not even Ctrl required) that's quite scary with confirmation dialogs

[CatsDeservePets]

Personally, I would not call it destructive. The worst thing that could have happened is moving the folder to a wrong place. To avoid deleting files by accident, the actual delete (not cut) command is unmapped by default and still requires confirmation.

If you prefer a more GUI like approach, you can put the following into your lfrc file:

# unmap default bindings
map y 
map d
map p

# replace with custom bindings
map <c-c> copy
map <c-x> cut
map <c-v> paste

You can find a full list of all default key bindings in our documentation. Inside lf, you can also press : to get into Command-line mode and type help to see the documentation.

[ratijas]

Personally, I would not call it destructive

deeply technically it may be the wrong term, but you know what I mean: no UI hints, no simple undo (maybe there is one, who knows, see the "no UI hints" point)

For clipboard buffer in particular, I like the copyparty approach: it gives a hint that something is in the clipboad, also asks before pasting

[CatsDeservePets]

deeply technically it may be the wrong term, but you know what I mean: no UI hints, no simple undo (maybe there is one, who knows, see the "no UI hints" point)

You do have a coloured number inside the statusline to indicate the amount of clipboard items and its mode. However, you obviously do have to know what it actually stands for.

I do agree that lf (and terminal file managers in general) aren't the most beginner friendly. lf was originally meant to be a lightweight and cross-platform clone of ranger. Most users these days either come from ranger or have been using lf for years. Both ranger and lf mainly target Vim users, which is reflected in their keybindings.
If you have little to no experience in either of these, they can feel foreign and confusing at first.

The docs include a beginner tutorial which explains the very basics. It is kinda old now but still applies.

I also totally understand that file operations inside terminal file managers can feel daunting. In the beginning, I used lf to quickly navigate through my files. However, I used to switch to a GUI to copy, delete and move files.

For clipboard buffer in particular, I like the copyparty approach: it gives a hint that something is in the clipboad, also asks before pasting

This can be achieved by overwriting the paste command with a custom shell command. This requires some tinkering and needs to be adjusted according to the OS and shell you are using. But doable.