A few mods use the extra inventory slots those provide. But currently when you die, those items get thrown on the ground instead. Support for those mods would be awesome, especially considering Better Graves doesn't have proper support either.

it's a bit annoying to still not have mod support for trinkets

PTOM76#3 PTOM76 seems to be the new maintainer of Gravestones on modrinth and I have made a PR, it was a fun little thing to figure out

Edit: Not perfect/not working with all trinkets

Gravestones does support Trinkets; it might not have seemed like it because the API was configured incorrectly on Gravestones' end in previous versions [it got fixed in 1.8].
As for Curios mods, I reported that issue months ago (#14). I assume it would require the implementation of the API on Gravestones, like Trinkets.