Select Already existing entries in a column without using mouse or having to check 'Filter' option:
Pressing Alt key and down arrow at the same time, shows the list of previously keyed-in entries, in that column.
For example.
In a particular column, suppose you are typing list of data : Names of Customers, and you want to check whether
a particular name is previously Keyed in or not, then, without having to use the filter option and check the drop
down values there , you can press Alt +↓ (down arrow) simultaneously, In the same cell, excel will show
the list of all unique values already keyed in.
Image of Alt+↓ Showing list values