/api/v0/object/patch/add-link replacement?

Given an IPFS UnixFS directory I need to add a new file to it. How can I do it if /api/v0/object/patch/add-link is deprecated? I need to add a small file from a browser to a very big directory, so re-uploading the whole thing is not an option. Is there a safe API to do it without messing with objects directly?

Thank you!