When sending a NFTs in bulk you are not given the option to mark the txn as a transfer. Below are two examples of a single NFT transaction that allows you to mark as a transfer, the second image is an example of multiple-NFTs without the option to mark as a transfer.
A workaround here would be to create a custom currency for each of these NFTs and recreate the transfer transaction as individual transactions per NFT. You will also need to update any transactions with the original version of those NFTs with the custom currency to ensure price history and cost basis remains accurate.
We have removed the option to mark as transfer to avoid confusion, our team is working on improving our bulk token and NFT support, once improved we will be re-adding this feature. Keep an eye out for updates!