"Custom" padstack mode just doesn't work in footprint editor

Description

Specifically in the footprint editor, the "custom" padstack mode functions identically to the "front/inner/back" padstack mode; there is no way to have different pad dimensions on different inner layers. When editing pads from the PCB editor, this is possible, but this doesn't allow you to make any custom padstacks in newly-created footprints, nor does it permit duplicating the customization to other footprints (at least as far as I can tell).

Steps to reproduce

1. Put a pad into "custom" padstack mode in the footprint editor.
2. Try to give it different dimensions on layers In1.Cu and In2.Cu--neither layer is even available for editing, just "inner layers".

KiCad Version

Application: KiCad Footprint Editor x64 on x64

Version: 9.0.7, release build

Libraries:
	wxWidgets 3.2.8
	FreeType 2.13.3
	HarfBuzz 12.2.0
	FontConfig 2.15.0
	libcurl/8.17.0-DEV Schannel zlib/1.3.1

Platform: Windows 10 (build 19045), 64-bit edition, 64 bit, Little endian, wxMSW
OpenGL: NVIDIA Corporation, NVIDIA GeForce GTX 1650/PCIe/SSE2, 4.6.0 NVIDIA 581.29

Build Info:
	Date: Jan  2 2026 01:00:49
	wxWidgets: 3.2.8 (wchar_t,wx containers)
	Boost: 1.89.0
	OCC: 7.9.2
	Curl: 8.17.0-DEV
	ngspice: 45.2
	Compiler: Visual C++ 1944 without C++ ABI
	KICAD_IPC_API=ON

Locale: 
	Lang: en_US
	Enc: UTF-8
	Num: 1,234.5
	Encoded кΩ丈: D0BACEA9E4B888 (sys), D0BACEA9E4B888 (utf8)