Hi @Heinz
Welcome to the KNIME community! I think there will be various ways to solve your problem, so i think in the end it might come down to personal preference and what you want to do with the information afterwards.
One suggestion would be to read the two excel sheets with two separate -Excel Reader- nodes, then use the -Extract Column Header- node on each of them. You could set this to extract column headers as a single column. Then you could use the -Joiner- node to do a full outer join and split between separate output ports.
Extract Column Header:
Joiner:
You can find the workflow on the hub here:
Hope that helps
Heather