Currently we can sort the records using a single-line text field but we cannot using the multiline text.
Would be nice to add that possibility 
I’m super curious about your use case here — what data would you have in a multiline text field that would result in a useful sort?
We use Dato for redaction of texts that are used in online chat conversations. For instance, our customer can redact “Goodmorning! :)” to “Goodmorning.” if she prefers that. We have thousands of these texts, so easy sorting, filtering and navigating these texts is crucial. Filtering works well, sorting and navigation do not - sorting is not possible currently, and navigation is annoying because of lack of pagination (Remove infinite scroll in favour of pagination)