1. Run TestApp from this repo(a54b7d5);
2. Drag and drop the right tabs(Tool Window 1+2) to the same float window;
3. Right click and hide Tool Window 1;
4. Drag and drop Tool Window 2 to the top of the MainWindow;
5. Click Tools/Tool Window 1

Expected:

It should still possbile to show Tool Window 1, either in an new float window or the same position as Tool Window 2;

Actual:

Tool Window 1 can not be shown, and see PreviousContainerId is missing from the output Layout.config;