MCEdit - MCEdit is an open source world editor for the popular game Minecraft.
Sodium Minecraft Mod - Sodium (for Fabric)
Schematica - Minecraft MOD - With this mod you're able to display a ghost image of a schematic file inside Minecraft to rebuild a structure or export any part of your world (or a server's world) into a schematic file. You're able to export parts of your world, too!
OptiFine - OptiFine is a mode that promises a significant boost to FPS for anyone playing Minecraft, whether they are online or offline, playing in single player or with other people.
WorldEdit - Minecraft MOD - WorldEdit is an easy-to-use in-game Minecraft map editor. Through a combination of commands and "brushes," you can sculpt your world or simply perform numerous terraforming tasks.
MultiMC - Overview: MultiMC is a free, open source launcher for Minecraft, managed by Forkk13and peterixxx...