I have attached a document that the DIAdem R&D team made available about 10 years ago that goes into more depth about the FFT functionality implemented in DIAdem. It does have some more detail about the FFT window functions, although maybe not to the level you may be interested in.
I hope this is helpful anyway,
Thank you for the reply!
I actually had this document already and it was useful. The window functions though are not given.
While many have "standard" names in Diadem and I can presume (...) they have standard parameters others are more obscure (like "Cos10Perc"; I guess coming from "cosine 10%" and the "10%" is the taper length but...). It is unfortunate that the functionality with different functions exists but the "trivial" part to make those functions explicitly known is missing. Now one is given the choice to eventually multiply their input with an unknown function (shape) and then analyze FFT results. Of course there is the "User" option which is good but less convenient.