Ok so sorry that I'm a bit late.
You first need to get a box character (there is a forum post for it, I'll link it) in the complex numbers mode.
Then you press right for 2 seconds and press left once. If the cursor leaves the box, you'll have to do this again.
Press right once.
Type 99 followed by a constant (press shift 7 1 1).
Type 99 again followed by a square root.
Press del once and then left three times, del three times and left 2 times.
It should be a box with 99 now.
There it is.
Btw the code lives in segment 0 while the ram + stack lives in segment 1. You can still do some kind of ROP.
The an symbol also seems to pop some registers and then PC from the stack.