[BRX]

I'm talking about the files tab in the edit screen and like to suggest a fifth way to add (especially additional) files to the song.

Please add an icon with the song picker (including filters) like at several other places in the app.
Also by using this file picker please let MSP not only add the file path and pages but also all the 
other annotations and especially crops to be used in the song it's added too.

If you want to merge songs from different files (for a medley or merging different versions, chords, lyrics for other reason) one can
save a lot of time and work if the annotations and crops are imported.

[Zubersoft]

I think you can accomplish what you are describing by using either the copy song feature or the "Create Snippet" feature. The snippet one also lets you choose which data you want present in the new song (metadata, annotations, etc).