We support two ways of creating Production Orders in batches.
One way is to create a new (virtual) high level Finished Good (say with SKU: ABC) and in its Bill Of Materials add the (real/existing) finished goods with the quantity you want to manufacture. Then, create the Production Order for the virtual product ABC and check the option to create the Production Orders for the child products automatically. See this article that explains the process. In the following screen, all the Production Orders for all the finished goods will be listed so, just delete the one for the virtual finished good ABC. You can see an example here.
Another way to create multiple Production Orders is by using the clipboard. Pin more than one Finished Goods in the Clipboard (see this article if you are not familiar with the Clipboard module) and then start a Production Order. In the following screen, select the Inventory Location and click the Clipboard icon and click Paste. The system will create multiple Production Orders for the Finished Goods that were in the Clipboard.