Inspired from T197841: Allow to append to the output page on category.py listify in this comment: T197841#4398603, seems it will be useful to have both options in the listify action?
Also, the patch: https://gerrit.wikimedia.org/r/c/pywikibot/core/+/462141 appends new category list at the bottom (by default) of the already existing page (using the -append option).
If we're going to implement both options, we should discuss their names :)
Suggestions
From pagefromfile.py, suggestions are to reuse -appendtop and -appendbottom options.