[bagim003]

The app can already almost do this, in the sorting dialogue in the top right of the library you can choose to sort by specific fields, but Composer isn't an option.

This means to actually sort by composer I need to go into the composer view, which is incredibly tedious for me, going into a specific subfolder for each composer. Most of my library is from different composers rather than a lot from the same (and I would guess the same goes for most people), which means each composer folder only has a small handful of individual pieces, so a subfolder structure doesn't make sense, and a complete list in composer order would more useful.  

I don't suggest the current composer view should be removed, I'm sure it must be useful to someone, just that the sorting dialogue be more refined with an option for composers added.

[itsme]

If you go to Settings - Library Settings - Song Title Formatting and specify a title format with the composer first, e.g. %COMPOSERS% - %TITLE% and check the checkbox "Use formatted title for sorting" in the sort options the list will be sorted by composer. Be aware that "Composers" is plural, it's a multi-value field - there might be surprises in the sort order.

With
%COMPOSERS:${VALUE} - %%TITLE%
you can avoid the preceding " - " in those cases where no composer is specified, but the sort order is a mix of titles and composers.