I loaded your EXCEL sheet expecting to see 1 record per client "LOD expression in Tableau to come up with a unique ID count" this is what I saw
Understand that you want to avoid a larger data set but don't really know why - 50000 or 500,000 records isn't all that big
Putting that aside - if you join your "enriched data file" to the base data (either rolled up at some level or disaggregate) on Customer ID
the enriched data will be tied to each customer record in the d/b
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