P: Sort by more fields, sort by multiple fields

I'd like to sort in Library by a metadata field that isn't offered in the Sort menu. Rather than asking for my favourite-of-the-day field to be added to the Sort, why not add the ability to sort by any metadata field, similar to the way LR allows filtering by any metadata field?

And/or, what about allowing sorting by a user-defined (via script?) function?

And/or by a user-provided query string.

(Extensibility makes products great/greater.)

LR current allows sorting of images by a single criterion, such as ordering by 'capture time' or 'filename' or 'rating'.

What happens if multiple photos have the same sort value, eg., rating? How are photos of the same sort value then 'sub-sorted'?

Typically this is handled by allowing multiple levels of sorting (eg., as Microsoft Excel does).

This would be even more valuable if LR supported sorting by any metadata field, eg., by title or GPS latitude or keyword-value (keyword-value pairs were supported, which I'll post separately as an idea).

Note that this could be implemented even in the current single-sorting-level paradigm by allowing sorting on values (-, 0, +) provided by user-defined scripts that would have read access to metadata. (The idea of supporting user-defined sort scripts was posted separately earlier.)

I agree that it would be good if LR let you sort on additional criteria.  

If your ultimate goal is to identify pics that are too small or too large, you can use smart collections with the Megapixels criterion, e.g.

Megapixels < 3.0

A couple of other plugins provide a little more flexibility in filtering by megapixels, but if you want to produce a collection that is correctly sorted by megapixels (cropped or uncropped), see the Data Explorer plugin.

Is it possible to add an additional sort feature to sort on megapixel size

Sorting
Having just switched to LR from iMatch (from PC to Mac) I was shocked and horrified to find LR cannot even do elementary sorting on (extended) IPTC fields. My shoots are of things that are presented in a particular order which may be significant (or not). These shoots can run into hundreds and sometimes even more than a thousand images; they are also spread out over time. I encode my objects using location conventions that are readily understood by others working in the same field (art history) and in order to tag this data and interpret it properly I need to be able to look at it in order. I would have thought this is pretty elementary but I have just learned that LR can only sort on fields that are of no interest to me at all (and somewhat superfluous in that files can be given names based on date and time). Ideally I would be able to sort on:
LocationCreated/Country
LocationCreated/City
LocationCreated/Sublocation
LocationShown/Sublocation (for location code)
Additionally, it would be very useful to be able to combine such sorts with one or more (hierarchical) keywords. In my case those that identify the object by type, because the same location can have different types of objects.

Since all of this info is already part of the database I find it incomprehensible that it cannot be put to good use. PLEASE implement decent sorting routines soon!

As a workaround for this lack of functionality, the List View plugin will let you sort lists of photos by multiple fields: http://www.photographers-toolbox.com/...