Tilemap Layer, how to make seamless tilesets on a single file?

Tilemap layer functions just create another tile, so far, what do I do? Because I don’t like copy pasting an individual tile on another file and doing things to make it seamless again and again

Prefer being able to do it on a single file

You should have nine tiles in a square (for just making sure it’s actually seamless), and your edit mode should be set to manual.