junegunn/fzf 0.41.0 on GitHub

Added color name preview-border and preview-scrollbar
Added new border style block which uses block elements
--scrollbar can take two characters, one for the main window, the other
for the preview window

Putting it altogether:

fzf-tmux -p 80% --padding 1,2 --preview 'bat --style=plain --color=always {}' \
    --color 'bg:237,bg+:235,gutter:237,border:238,scrollbar:236' \
    --color 'preview-bg:235,preview-border:236,preview-scrollbar:234' \
    --preview-window 'border-block' --border block --scrollbar '▌▐'

Bug fixes and improvements