Inserting Data into Formatted Tables
I was recently working with a large Formatted Table in excess of 100,000 rows with Power Query.
I was copying in new data to a temporary workings table and then manipulating it with Power Query to get the required output. The data was varying lengths. I found that if you pasted data into a Formatted Table that was a lot longer than the Formatted Table it can take a long time for Excel to process the paste (I am talking tens of thousands of extra rows).
To get around this delay I found that if you first expanded the Formatted Table using Insert Rows, the paste was virtually instantaneous. Inserting the extra rows was also very quick.
So if your Table has sufficient rows the paste is quick, if Excel needs to expand the table to fit the new data, it can be slow for large data sets. Make sure you insert sufficient blank rows to speed up the paste.
You can learn more about Formatted Tables at the two blog posts below. I have also covered the topic in numerous free webinars.