Describe the bug

Using set fzf_preview_dir_cmd exa --all --color=always or set fzf_preview_file_cmd cat -n in config.fish has no effect on the actual preview.

To fix this I needed to use set --export fzf_preview_dir_cmd exa --all --color=always instead.

Steps to reproduce

1. Add set fzf_preview_dir_cmd exa --all --color=always to your config.fish
2. Start new shell so that config.fish gets sourced
3. Press Ctrl+Alt+F
4. Get no colored exa output but the plain ls -F -A output that's default

Environment

Versions installed:

• Fish: 3.6.1
• fzf.fish: 9.9
• terminal: alacritty 0.12.2 (9d9982df)
• OS: Linux, EndeavourOS, kernel 6.4.10-arch1-1
• Configuration variables:

set fzf_directory_opts --bind "ctrl-o:execute($EDITOR {} &>/dev/tty)"
set fzf_preview_dir_cmd exa --all --color=always
fzf_configure_bindings --git_log=\e\cg

Additional context

Fix

This can easily fixed by adding set --export the the variables.
Is this intentionally? If so I would propose to add this to the documentation.