You will need to install a user script manager extension to install this script.
As you may know, Mangaupdates.com has a Series Genre Search. Sadly, it doesn't remember your choices, so if you're regularily searching for new manga to read, you have to re-enter them every time.
This Userscript lets you pre-define those choices (at the beginning of the source of this script), which it will then always select whenever you open the search form for the Series Genre Search.
It also opens the search results in a new Tab/Window per default, but that's also a changeable option.
At some point I might edit this userscript so you can tell your browser to remember your current choices rather than having to edit them into the script, but for now I'm satisfied with this (I primarily made this for myself, and uploading it here is primarily a way of backing it up).