I haven't found a way to modify the fuel list of the SemiFluidGenerator with IC2 config files.
So having support for that in ModTweaker would be really nice.

• Minecraft: 1.12.2
• Forge: 14.23.1.2559
• Crafttweaker: 1.12-4.0.10
• ModTweaker: 4.0.5
• MTLib: 3.0.1
• IC2: 2.8.16-ex112

If the config can't change it, then we can't