I am trying to create a new "Lot Numbered Assembly/Bill of Materials" item, but I do not see it as an option when creating a new item. However, I can create a "Lot Numbered Inventory Item". Do I not have a certain feature enabled for "Lot Numbered Assembly/Bill of Materials" to show up?

Apart from enabling Tracking feature, check if you have enabled Assembly Items. Setup > Company > Enable Features > Items & Inventory tab > Assembly Items

"Lot Tracking" is enabled. However, I do not have/see an "Assembly Items" feature to enable

It sounds like you have the Inventory Management module, but you do not have the Work Orders and Assemblies module in your NetSuite Account. Did you specify a requirement to have Assemblies when going through your NS requirements?

That looks to be the case. Thanks for your help.