Merge two columns/lists into new single column/list removing duplicates (formula)

Hi All,

I have two columns of data. I'd like to merge the two columns into a new single column which would contain only unique values. I need a non-array formula that will do the work (e.g. I cannot use advanced filtering). Here are some conditions that may also be useful to know:
1) Within the two data columns, all entries are unique. The duplicates exist across the two data columns.
2) The data columns are created programmatically. The number of rows of data in each column can therefore change. I have created dynamic named ranges that adjust to the length of each data range called List1 and List2.
3) If it helps, I can add helper columns to either data column, although my preference would be to avoid this.

NOTE: post edited to add requirement that formula not use array formulas.

Thanks,
John

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