Looks like you can add additional Modal Frames in the component tree, just make sure to disable the "close when clicking outside" checkbox. I still think this is unintentional UX, but it works for now.
Coming back with a quick update! The Legacy Modal component is now deprecated and the current version is the Modal Frame. You can still open a modal from a table row and even place another table inside that modal. Here is a screenshot and here is another topic that walks through how to open a modal from a table row.