The only reason I make Planks or Silks is to reduce the number of tokens lying around. They have so little value.
So, there's planning what you are going to use and there's "cutting weight". Transmuting for trade goods just to do it doesn't strike me as better than keeping the components. Sometimes, weird tokens can get hot, especially with VTD, where weird runs are far easier.
But, as for very broad thoughts on what to hold on to even when in cut weight mode, participation tokens, treasure box only tokens (gee, suggestion to have these two types in different colors aligns to something), rez potions, Scrolls that do something "important" (Stone to Flesh, Mind Blank), interesting ammunition because EMs are used in such small quantities anyway, far better than their rarity tokens like Linked Shirt of Healing, named recipe components.
I used to like to hold on to lots of potions I would never use, but Ink is like the one thing I can run out of on my own, so lots of healing potions went away a while back, as did I'm sure Dex/Str potions. With Iktomi's, polymorph potions aren't as consumable so need way fewer, though, oddly, not everyone has Iktomi's (yet).