Hold down the down arrow key until the cursor gets to where you want. You don't need to keep pressing/depressing the arrow key.
Alternatively, If it's an LBC drop-down menu list, then just type the first letter of the name in the list (e.g., "S") and the cursor will jump to the first occurrence. Pressing "S" again will jump to the next line beginning with "S", etc.
Otherwise, you could use an AutoHotkey script, I suppose, but it would seem kinda pointless (forgive the pun).