This won't work in the template view, but we figured out that by adding a custom integer attribute field that we could modify the Order By string in the category list module settings to sort on that custom field and thus to create an ad hoc sorting mechanism.
We created a new custom field name "SortOrder" and for all documents we can number them accordingly such as 10, 20, 40, 30, etc. Then in the settings for the category module we add:
>> SortOrder, LastModified DESC, Title (or use whatever other fields are desired for sorting)
This works well for us now. My only request for a future release would be the ability to add a "default" field for any custom attribute. For example, in this case I'd like to be able to set a default of "9999" so the default sort order would fall back to the LastModified date unless specific sort order values lower than that are entered. I could probably order by "SortOrder DESC" and enter my sort values from high to low which would let all those with null go the bottom of the sort, but that would not be as intuitive for our end users.
I thought I might be able to add a default for some specific column directly in the database somewhere but apparently it isn't that easy. If that IS possible, please let me know. Otherwise, consider it an enhancement suggestion.