I know there are plug-ins that will sort open files and tabs by file name but AFAIK they are linked together. If the open files are sorted alphabetically the tabs are sorted alphabetically. I am often switching between just a few files while having many more open. I like to keep the files I'm working on together in the tabs but if I need to jump to another open file it would be much easier to find it if the files were sorted alphabetically in the side bar - but I don't want to disturb the order of the tabs!
TL;DR: Sorting of open files in the side bar should be separate from the sorting of the tabs.