I created this after the user ikwyl6 wanted a quick way to filter the buflist
/set buflist.look.display_conditions "${eval_cond:${plugins.var.buflist_conditions}} && ${buffer.hidden}==0"
/alias add search_buflist /set plugins.var.buflist_conditions $1-;/buflist refresh
/alias add search_bufname /search_buflist ${channel}=~$1
exemples
display buffer with more than 50 users
/search_buflist ${irc_channel.nicks_count}>50
display buffers with hotlist
/search_buflist ${hotlist}
display buffers with a priority of highlight
/search_buflist ${hotlist_priority} == message
display channels with wee in their names
/search_bufname wee
to show everything
/search_buflist 1
or
/search_bufname .*