Use the touchscreen brush and selection tools to alter the terrain, spawn structures, or tweak world parameters.
Remember that different world sizes (Small, Medium, Large) have different total tile counts, ranging from terraria map editor mobile free
Instead of painstakingly drawing a lake on a map editor, you simply give your character 999 "Water Buckets" or an "Infinite Water Bucket" and dig the lake yourself in-game. It is faster and far less prone to file corruption than trying to edit the world geometry directly on a phone screen. Use the touchscreen brush and selection tools to