It actually is the one at $009250. SMW only calls the routine on power-on, but leaves the HDMA in channel 7 so it continues to be used.
(if you ever write another DMA to channel 7, it ends up getting bombed)
To clarify, here's the table it writes, in a more clear format:
DMAWindowData: ;$009277 | Windowing DMA settings and data, stored to $4370-$4374. db $41,$26 ; Translation: write data pointed to by $00927C to $2126/$2127 (window left/right positions). dl $00927C DATA_00927C ; $00927C | Pointers to the windowing data in RAM. db $F0 : dw $04A0 db $F0 : dw $0580 db $00
Professional frame-by-frame time wizard. YouTube - Twitter - SMW Glitch List - SMW Randomizer