put "foldl" and "foldr" in "Useful";
Isabelle hides those symbols from List, but by adding them to Useful we have them throughout Metis without "List." prefix
;;; Options for Proof General
;; Examples for sensible settings:
(custom-set-variables '(indent-tabs-mode nil))
;(custom-set-variables '(isar-eta-contract nil))
;(custom-set-faces
; '(proof-locked-face
; ((((type x) (class color) (background light)) (:background "lightsteelblue2")))))