sudo apt-get install geany geany-plugins
In the screenshot, you can see the useful vertical and horizontal scrollbars. If you go to edit > preferences > keybindings there are a massive number of options, and, according to the FAQ,
geany uses standard GTK+ keybindings. Virtually every action in the editor can be assigned to a key, so I think you will be able to set it up as you wish.
In the screenshot below, I have opened a python script (originally from this site) in which I am trying to fix a problem in the way it parses ustream urls. As you can see, both syntax highlighting and some code suggestion/completion is built into the program: