I don’t believe that’s a change we’re considering at this time, but if there’s a use case for it, please feel free to work with partner or customer support and enter an idea.
@ian.p’s suggestions are all correct and will lead you in the right direction for getting the right record(s), so long as the subtable is of type Main. If not, the Fetch suggestion will not work.
If what you’re working on is early enough in the development process, you can always consider a different data structure like a Header-Detail or manually controlling the relationships between tables. Many things are possible, so feel free to post more details or clarifying questions about what the most performant solution might be.
There’s also this thread, Is it possible to sort a sub table?, which goes into some more detail on the matter.