The reason I ask because I sometimes convert 5e material to 4e. So I want to know the relative power of a monster in relation to the PCs. I generally to that assuming that what a system says about itself is true. So for conversions from 1e I use monster XP, for 3e I use CR.
For 5e I've been calculating the encounter XP, and assuming that the minimum threshhold for "deadly" corresponds roughly to the level of PC. So for instance if a single creature is worth XP 10,900, I convert that as a solo monster of 19th level; whereas if 4-5 monsters are worth 10,900, I convert them as 19th level standard monsters (it's a bit more complicated than that, but you get the gist). The results have been unexpectedly consistent. But I have no way of doing that for any creature with a CR larger than 15.
So an extended chart would have been helpful, even if it doesn't really work that way in practice. I have tried just following the pattern of XP increases on the chart, and that has worked... ok, but something official would be better.