That 2da is the list of all available item properties, you can add lines making reference to feats.2da, take Dodge item property as an example to copy and learn how to use it, youll see that there is a number at the end of the Dodge item property, which is the same number you can find in feats.2da for dodge feat.
if your crafting menu scripts pull all item properties from 2da, you should be able to see the recently added item properties!
and yes, you should be able to delete item property feat lines, tho, its not recommended!
hope this helps