I was working on a category in my new world. I wanted to structure the sub categories and a few articles in a similar matter do a previous world I had worked on. I was in the "old editor" of my category, I then opened a new tab of WA (using dab duplicate and then switching in the duplicated tab) and switch to the other world, found the BBCode I had previously used, Copied it and pasted into my category I was working on, switching the tags and url to the correct ones. after saving and viewing the world, it showed it as if that category was in the old world,
1: open old editor for a category in world 1 2: open a second tab of world anvil (dublicte 1st tab) and switch to another world 3: open old editor for a category in world 2 4: copy contents from world 2 category and past to world 1 category. 5: save changes in world 1 and open the world View
You should never have two worlds open at the same time. This is not a bug it is a misuse of the system.