This answer is only partially correct. I am on Desktop Enterprise Solutions Manufacturing and Wholesale 24.0

First, in order to change the COGS you have to be in single user mode.

Second, when I try to change the COGS I get a dialog box

"You changed an account associated with this item xxx. All future transactions with this item will use this new account. Would you like to also update existing transactions? Yes, No or Cancel"

This question seems to imply that it is possible to ONLY CHANGE FUTURE TRANSACTIONS....

However, when I choose NO (meaning I do NOT want to update existing transactions), then I get the message "This modification will affect transactions from closed periods" which seems to directly contradict the instructions from the prior dialog box. This appears to be a bug in the software. It appears to offer you the opportunity to only affect future transactions, and then does not do it....!