Is there a limit to the number of fuel types (or lines/rows) that can are presented in the GUI?

Fuel types (e.g. LFO), or resources?

Either way, it should be unlimited. Adding more will push the rest of the GUI elements downward.

Like LFO / Hydrolox that will add multiple fuels at once.

OK, thanks! I have exactly all lines filled and a new type was not showing up, so I was not sure if there is a max number of lines (at 4 now I think). I'll check what I am doing wrong on the new fueltype then (MKS with 27 resources inside).