There's lots of unknown stuff around $143E through $1456. I'm pretty sure all of it is related to the various autoscroll commands, but according to the RAM map, it is also used by the credits. It is unknown how much of it has these meanings for all scroll commands.
I could gather the following from inspecting scroll command 8, which scrolls layer 2 back and forth (used in Morton's castle), in all.log:
$143E -
Scroll command number, known
$143F - Secondary scroll command (often affects layer 2 while the primary one affects L1, it is unknown how often it has another value than $143E)
$1440 - The starting Y-position of the current scroll sprite, left-shifted twice, with the extra bits added to them.
$1441 - Same as $1440, but used by the secondary scroll command. It is unknown if this ever has another value than $1440.
$1442 - Layer 1 direction?
$1443 - Layer 2 direction?
$1444 - Unknown, likely used by the primary scroll command in other scroll commands
$1445 - Unknown, likely used by the secondary scroll command in other scroll commands
$1446 - Layer 1 X speed, 256ths of a pixel (16 bits)
$1448 - Unknown, used by the primary scroll command (16 bits)
$144A - Layer 2 X speed, 256ths of a pixel (16 bits)
$144C - Unknown, used by the secondary scroll command (16 bits)
$144E - Fraction bits for layer 1 X position, 256ths of a pixel. The high byte is always 00. (16 bits)
$1450 - Unknown, used by the primary scroll command (16 bits)
$1452 - Fraction bits for layer 2 X position, 256ths of a pixel. The high byte is always 00. (16 bits)
$1454 - Unknown, used by the secondary scroll command (16 bits)
$1456 - Current layer being processed by autoscroll sprite (#$00 = layer 1, #$04 = layer 2)
If someone thinks this is useful enough to send to the RAM map, feel free to.
<blm> zsnes users are the flatearthers of emulation