We support two ways of creating Work 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 Work Order for the virtual product ABC and check the option to create the Work Orders for the child products automatically. See this article that explains the process. In the following screen, all the Work Orders for all the finished goods will be listed. Delete the one for the virtual finished good ABC.
Another way to create multiple Work 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 click MANUFACTURE > Work Order. In the following screen, select the Inventory Location and click the Clipboard icon and click Paste. The system will create multiple Work Orders for the Finished Goods that were in the Clipboard.