Feature Request: allow functionality of fzf --preview similar to fzf-tab

[ahgraber]

[EDITED] I'd like to be able to preview the directory that is being completed (especially using cd or ls, but a generalization could also be very useful). With fzf-tab, I used: zstyle ':fzf-tab:complete:cd:*' fzf-preview 'exa -1 --color=always $realpath'

zsh4humans doesn't have an equivalent of this option.

Originally posted by @romkatv in #35 (comment)