Unable to reattach Blueprint Viewport to main window

Hello to the ones that read this,
I’ve pulled the blueprint viewport tab out of the main window and now I can’t reattach it to it.
There is also no tab or default window bar in the viewport window. The small yellow triangle in the upper left corner only opens the default windows menu.
Could anyone help me with this because it’s quite uncomfortable to work like this?

Greetings
RRe36