1. Tab to Last Name.
2. Enter first few characters of last name until last name is found.
3. Tab to First Name, then Shift-Tab back to Last Name.
Listing will now be sorted by Last Name, and First Name within Last Name. You can page up/down or scroll through the list in alphabetic order by first name.
If you have a large number of customers in your database, you may prefer the Find option to locate customers. You can set this as the default search in Manager under File, Configuration, Options, Customer Options, Always display "Find" window. However, the above routine is for Lookup not Find. To sort by Last/First in Find you would need to fully enter the last name you want to search by, check off Last Name search only, then click on the First Name column.
If above options are insufficient, consider our V.I.P. Zone add-in which provides automatic last/first name sort and much more.