Showing more than 10 items would be harder than expected because there are raw arrays of size 10 declared in the CCSWnd_List class.
Code:
00000000 CCSWnd_List struc ; (sizeof=0xCE8, align=0x4, copyof_3148)
00000000 ; XREF: CCashShop/r
00000000 baseclass_0 CWnd ?
00000080 m_pSelector ZRef<CCtrlSelector> ?
00000088 m_pBtPlate ZRef<CCtrlButton> 30 dup(?)
00000178 m_pBtShortcut ZRef<CCtrlButton> ?
00000180 m_nPlateNo dd ?
00000184 m_nPlateFocus dd ?
00000188 m_nButtonFocus dd ?
0000018C m_nCommodityIndex dd 10 dup(?)
000001B4 m_nStockIndex dd 10 dup(?)
000001DC m_nLimitGoodsIndex dd 10 dup(?)
00000204 m_nGender dd 10 dup(?)
0000022C m_bCannotBuy dd 10 dup(?)
Also notice the array of 30 buttons (3 for each item). This is the v95 structure but it's the same idea in v83. There isn't enough room in CCSWnd_List to show more than 10 items at once and any solution to that would need entire functions to be rewritten (or dozens of codecaves, but thats very unsafe and isn't much easier).
Idk if you need this but for the cash shop inventory try changing the instruction at 0x4B040D. It's lea eax,[eax+eax*2+06], change to lea eax,[eax+eax*2+x] where x is half the number of items you wanna show (im guessing 14).
For the item inventory the number of slots shown is in 0x4B1AA6. There's probably more you need to change but you can take a look around that address and figure it out. (The function is called CCSWnd_Inventory::Draw.) The function 0x4B1E69 (CCSWnd_Inventory::GetItemSlotRect) does some of the math for drawing the inventory.