I wanted to make the same request. I download a lot of audio books from Audible and the folders and filenames are named by Audible like this: <artist> - Episode 1 - <title>. In Poweramp, right after this folder comes <artist> - Episode 10 - <title>.
I have hundreds of folders named this way because they are named like this by Audible. There are even audio books with over hundred episodes. I don't want to rename every folder manually after I download it and I also don't want to rename every file manually. This would take days! For example in Windows 10 the sorting is correct (Episode 1, Episode 2,..., Episode 10). Plus it doesn't look and read good to have something like "Episode 001".
Isn't it possible to have the option to change the sorting to numeric instead of lexicographic?