Hallo,
the scanning daemon is able to do this right now, so it's a GUI's limitation only (and in the fact, daemon normally scans in parallel incoming mails, modified files and on-demand stuff).
but, it's quite questionable how to present such results and keep the relative simplicity of the gui. we might add scanlist-tabs (one possibility), but most people do the on-demand thorough scan only ocassionally so I'm not sure whether this feature would be utilised by significant amount of users...
regards,
PC