I found the 2 crown “jump boost” schematic and I have the needed resources, but the crafting station only lets me apply the 1 crown jump boost schematic? -
If I attempt to use the 2 crown boost it says “not enough resources”
You have to have the shoes at the bottom of the crafting resource list to craft 
You need to 1st craft the 1* schematic before you can craft 2* schematic on top of it.
This goes with all apparel schematics. For example: if you want to craft 5* bullet resistance jacket, you have to craft 1*, then 2*, then 3*, then 4* before you are able to craft 5* schematic.
There are no shortcuts in apparel crafting.
thank you all, stacking seems to be the way - I did get the 3% jump boost eventually!
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With question answered, i’ll lock this topic. 
//Mod