Generate list of items by selecting one variable from validation list

Hello,

I'm new to the forums and have a basic question about best practices. I have a large inventory list which I am trying to create some assembly lists with. Ideally I'd like to be able to select multiple assemblies from multiple drop downs on a data entry page, and have a list of all the inventory parts in the selected assemblies be generated on another page. i.e:

Assembly A contains parts 1,2 and 3.
Assembly B contains parts 11,12 and 13
Inventory list has parts 1-1000 with unique serial numbers

When selecting Assembly A and Assembly B from data entry page, list is populated on pick list page

1
2
3
11
12
13

Rest of inventory list is omitted

My question is what is are the best practice methods for doing something like this? I can see multiple approaches such as VLOOKUP and INDEX functions, VBA scripts, etc. I'm trying to achieve a scale-able outcome that allows addition of an infinite number of assemblies and parts on the inventory list. Any insight you can provide are appreciated.

I have created a quick dropdown (attached) with a HLOOKUP to populate cells depending on the selection of the dropdown. This can be extended accross and down, but it may get you started.