Minecraft Snapshots are experimental updates that fix a variety of issues, usually in relation to the most recently released final numbered update. This snapshot of 20W30A focuses heavily on fixing a respawning that is used by one of the newest blocks in Minecraft, the Respawn Anchor.
The Respawn Anchor allows players to respawn in the Nether; this block was added in the most recent Nether Update. This block will enable players to respawn in the Nether instead of in the overworld; this block is crafted using six Crying Obisidian and three Glowstone.
This snapshot changes how the Respawn Anchor works, and this snapshot modifies how to respawn positions are chosen for beds and respawn anchors. This makes the respawn anchor preferred when killed in the Nether and when that respawn anchor is charged with Glowstone.
Some specifics on how Respawn Block positions have been re-worked by having a respawn anchors prioritize cardinal directions rather than corners. In addition to that, respawning players will now face the block that they respawned at.
In addition to the Respawn Block fixes, respawning, in general, has been re-worked. Beds will now prioritize the side of the bed that the player entered in the bed. Then after that, the spaces circle around the foot of the bed to the head of the bed.
Another huge fix to respawning or waking up, now when the game is trying to place the player in non-dangerous locations, this stops the issue that has plagues aesthetically designed builders for years. That issue is having the player wake up trapped in a block, and this is especially important to adventure maps and adventure map makers.
This snapshot also adds some gameplay changes as well, like Laterns and Soul Laterns can be waterlogged. Some other gameplay changes include tweaking the Bastion Remnant chest loot, and the chests in Bastion Remnants are now much more likely to be located on top of gilded Blackstone.
In addition to those gameplay changes, there have been some technical changes, some of which include the sign edit screen can now be initialized from already existing sign text. Mojang stated that this should have no noticeable impact on vanilla.
Another technical change is that tags can now have optional entries, allowing for much more customizability.