It's possible to read and write from entities and items in hand, but it's currently not possible with blocks.

This would allow for modifying slates in spell circles on the fly (at least in a more practical way)
it would also allow for integrations with pedestals from other mods as an alternative to item frames
and finally would be useful for addons lol

Writing to Scrolls in world would also be quite nice <3 I could do "/patterns hex" in game!

I am planning for messing with blocks to be the purview of spell circles, this is pending the giant casting context refactor.

This post was prior HexGloop. Though being part of the base mod would be nice.

I semi purposefully haven't implemented any direct read/write block stuff in hexgloop since idk if it'd fit best in moreiotas, base hex, or just in gloop. Currently gloop just has pedestals which hold a non-despawning item entity and it has a framework for block reading/writing with loci, but nothing useable yet.

I think this is pretty well covered by HexGloop - does it still need to be in the base mod?

Me and Sam talked about this a bit ago, and I think we decided a good way to implement this from a player perspective would be to allow passing a vector into the Chronicler patterns to read from / write to the block at that position.