Can you do a bulk csv upload of a single column of data?

Yes. In the products csv upload we'll just need the ProductId (which must match the products you're updating) and the column to update. Eg updating the lead time we'll just need a csv file of 2 columns ProductId, LeadTime.

You can also upload as many columns as you want (eg: updating the LeadTime, MinimumOrderQuantity, and StockOnHand) will require a csv file with columns ProductId,LeadTime,MinimumOrderQuantity,StockOnHand.

Any existing data related to columns not included in the file will remain the same.

Note: Updating a column with all rows blank will clear out all that data. So only do this if you deliberately want to clear that data.