Since numista did so many nice adjustments lately, I think it's time for this:
I suggest sorting by series, for example some issuers have ambiguous KM# and some XX century coins get mixed with XIX century because one specific old coin has a lately added KM#, and if I sort them by Catalogue reference, they get mixed.
If I want to sort them by Date, could be also a problem (example: 1 cent minted 2001, 2 cents minted 2005, 5 cents minted 2001 and in 2005 another coin series was released) because in many series happens, and the newly 2005 issued coins will get mixed with the 2001-2005 series, so I cannot sort them the way I'd like.
Examples could continue for all sorting systems, so I suggest adding Series sorting system where coins and banknotes could be added to a specific series and when searching by series they can appear like that for example:
Series 2001-2005 (or some alternative name)
#1 - 1 Cent 2001 (coin)
#2 - 2 Cents 2005 (coin)
#3 - 5 Cents 2001 (coin)
#4 - 1 Dollar 2002 (banknote)
Series 2005-2010
#5 - 1 Cent 2005 (new series)
#6 - 2 Cents 2005 (new series)
etc.