Is it possible to detach the terminal window from VSCode?
I do not think it is possible to open the integrated terminal (or anything in the panel) in a new window directly. If you do not want to use an external terminal you could:
make the terminal its' smallest possible size and maximize it using the "^" button (Image of the ^ button) on demand. You can also set a shortcut for
workbench.action.toggleMaximizedPanelto achieve this more efficiently.
create a new VSCode Window and only work with the panel / integrated terminal in the new window.
I suggest to simply not to use the built in terminal, but open a standalone one out of VS Code.
You can use any terminal you want.