Cheers. I must just be an idiot but I can't for the life of me figure out how. I deleted the Loading and Menu parts in the S folder successfully in ADF Opus (tried both V1.2 and the 2025 version), but when I edit Startup-Sequence, it immediately reverts to what it was before as soon as I hit Return or click OK. In the 2025 version it won't let me change the contents even temporarily. (The "Writeable" box is ticked and the ADF file isn't marked Read-only.)
I can delete Startup-Sequence entirely but then there's no way I can find to add a new version. I tried creating a plain text file called Startup-Sequence.txt, removing the suffix and dropping it into the S folder but it wouldn't recognise it ("unknown device type").