A better alternative for source code file browsing than finder+quicklook?
BBEdit is able to have multiple documents open at one time and then there is a left side sidebar you can easily change between documents. In the menu bar go to VIEW > Show Sidebar. It appears to keep your highlights and scrolling of each document. You can use BBEdit for free without paying for it as well but it will ask for you to pay for the first couple weeks. BBEdit has markers, grep find/replace, and multi-file search as well. Sounds like a lot of what you want.