Thanks for the feedback! This is a planned feature.
120 karma · joined May 29, 2015
Yes I'm planning to add City/Location filters as well as advanced search option where you can see all available filters.
There is for example also https://startupdeveloperjobs.com/f/0/Erlang but you can't see it since it has not enough jobs
Edit: To answer your other question. Jobs are both entered by companies and also added by me manually.