Various input methods of various kinds of media place apps and files in many different places. Therefore, I use the app Link2SD to move moveable apps to my microSD card and the app ES File Explorer to find and move files to preferred locations, both on and off my devices.
With ES File Explorer, I find especially helpful:
- the app's Homepage, where one can find and manage files the app classifies as "images", "music", "movies", "documents", and "app"
- the app's search function
- the ability to move files around (except when the Android OS prohibits desired moves, which moves I then can often make by connecting my device to my computer)
FYI, I like to store all of my sideloaded documents and books in Calibre Companion. I can then read via compatible apps, e.g., Moon+ Reader Pro.