Runic to Shock

As dn pointed out, to make a replacement, just edit one entry in each of these two table.

Code:

(Data - commands that can be replaced with other commands thanks to Relics)

C2/5452: 05   (Steal)
C2/5453: 0F   (Slot)
C2/5454: 0D   (Sketch)
C2/5455: 02   (Magic)
C2/5456: 00   (Fight)


(Data - commands that can replace above commands due to Relics)

C2/5457: 06   (Capture)
C2/5458: 18   (GP Rain)
C2/5459: 0E   (Control)
C2/545A: 17   (X-Magic)
C2/545B: 16   (Jump)

If you want to add entries, you need to relocate in bank $C2 preferably the two tables and edit the following code. Note that there is a free space block starting at C2/6469 but General Leo Edition maybe use part of it due to patches and such.

Code:

C2/53AB: A9 04        LDA #$04
C2/53AD: 85 EE        STA $EE        (start checking Bit 2 of variable $11D6)
C2/53AF: BF 52 54 C2  LDA $C25452,X  (commands that can be changed FROM)
C2/53B3: C3 01        CMP $01,S      (is current command one of those commands?)
C2/53B5: D0 0D        BNE $53C4      (branch if not)
C2/53B7: AD D6 11     LDA $11D6     (check Battle Effects 1 byte.
                                     Bit 2 = Fight -> Jump, Bit 3 = Magic -> X-Magic,
                                     Bit 4 = Sketch -> Control, Bit 5 = Slot -> GP Rain,
                                     Bit 6 = Steal -> Capture)
                
C2/53BA: 24 EE        BIT $EE
C2/53BC: F0 06        BEQ $53C4
C2/53BE: BF 57 54 C2  LDA $C25457,X   (commands to change TO)
C2/53C2: 83 01        STA $01,S       (replace command on stack)

To make a proper expansion, you'll need an item data bit. The existing swaps are on byte 10 ($11D6) but there is a free spot on byte 11 ($11D7:1). You'll need to tweak the above code to check for $11D7 as well:

Code:

(battle effects 1 and "status effects 2".  latter is nothing to do with status ailments.
11D6:
01: Increase Preemptive Atk chance  10: Sketch -> Control
02: Prevent Back/Pincer attacks     20: Slot -> GP Rain
    (this won't work for battles
     where back/pincer are forced)
04: Fight -> Jump                   40: Steal -> Capture
08: Magic -> X-Magic                80: Jump continuously

11D7:
01: Increase Steal Rate         10: 100% Hit Rate
02: --                          20: Halve MP Consumption
04: Increase Sketch Rate        40: Reduce MP Consumption to 1
08: Increase Control Rate       80: Raise Vigor