Copy the file ctags_for_gap to ~/.ctags and then run
  ctags --sort=no lib/*.g lib/*.gi lib/*.gd src/*
in the GAP installation directory. Start your editor
in that directory and then do (for vim e.g.):
  :tag DerivedSubgroup
(say). You can also use
  :ts DerivedSubgroup
to get an overview over all tags found (which is useful since it shows
for example all method installations).
