I wonder what's the use of Z-addressing ...

An example of z-address earthquakes (and scrolling) can be seen here:

Nah, it used an ASM lib that did the Z-address manipulation.

$0C is normal mode, I think $0D is vertical mirror and $0E is horizontal mirror, but $0D and $0E might be the other way around. $0F is mirrored both horizontally and vertically or rotated 180°).
It simply works by sending those instructions to the display driver (out ($10), $0F)
But those instructions only work on calcs with the new LCD driver. That might be a reason why it wouldn't be added to AXE.

Z-addressing does work on my calc, but not screen mirroring. I assume that I've the old LCD.

Anyway, now I got a feature request : some way to mirror a screen buffer

It would be nice if you could import a binary file as inline assembly. This would allow easier use of Mimas.

I've got 3 more things to ask.
1. I think I've found an optimisation for comparing an expression with a constant, to check whatever it is bigger or equal to it, or whatever it is smaller. This should be a start of it:
≥≥B should be the same (but larger) as -B<(32768-B) where I use 2 times a minus simple to substract, not to invert, and where 32768-B is being calculated at compile time, since b is a constant.
now, since <<B is the opposite, it should be the same as -B≥(32768-B)
This comprimises a few bytes, however, check whatever this may indeed be done first.
2. I'd like a function that makes a signed 2 byte value out of a 1 byte signed value.
I know this can be easily done by, for example, the following structure:
→Ae0?A+65380→A
and then A holds the value, but I'd like a more compact version of it that can be written in 1 function and only costs 4 bytes of space.
The assembly would look like this:
ld a,l
add a,a
sbc a,a
ld h,a
This would be a feature I would use all the time, because I save a lot of data, like speed, in a single byte, but need to add it to a double byte value, the position
3. It seems that the Disp command doesn't work very well if you have MATHPRINT turned on.
When trying to draw a number, it draws it kind of diagonally and it only draws the first character of strings.
This is at least what I've made up out of some tests.

1. I'm quite certain Axe already does this.
2. If you want to sign extend Aʳ just do sign{°A}.