look up semicolon seperated text from another table without split function

I think we can do this more simply than Vijay_A_Verma suggests.

Take the first element of the intersection of Table2[Prod List] and the products in the current row.

List.First(List.Intersect({Table2[Prod List], Text.Split([Product], ";")}))

Here's a fully self-contained variation of this query:

let
    Table1 = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCkgsKEisTFRIL0pNzbN2LCjISdXwTizOyM0s0lSK1UFX4J1ZnqmgEZqSmKegEVySmJei4JiTn5eqiU2tV2JytrV/UWJeeioW2YD83HygGampKTmpxcXYTHNKzANCBY2g1BSgQCwA", BinaryEncoding.Base64), Compression.Deflate)), type table [Product = (type text)]),
    Table2 = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("bcxBCsIwEIXhq4SuUvASVUGwC4viqnTxaB61mExCUije3pC4lNl8/MzMODZXzO9mOoxNF4Kl7pFebo1tSWdsTEWnnLkXDggBH6glklJKv+6r0k8DUfqxQYzqrBe29ckRkkfpO00Ng3c+L5LGMqV/J5bO19eO9qdLRGDRDKm4RciSOX0B", BinaryEncoding.Base64), Compression.Deflate)), type table [#"Prod List" = (type text)]),
    ProdList = List.Buffer(Table2[Prod List]),
    #"Added Custom" = Table.AddColumn(Table1, "Mapped Product List", each
        let
            CurrRowProds = Text.Split([Product], ";"),
            SharedProds = List.Intersect({ProdList, CurrRowProds})
        in
            List.First(SharedProds),
        type text
    )
in
    #"Added Custom"