If you've missed the corner while creating your floor plan or feel like that apartment might better work with an additional niche – that can be easily done with Planner 5D.
Determine which wall should have an additional corner. You'll need to break that wall into three pieces with the Split option and then drag the corner out like that:
You can now adjust the wall length to create the corner you need.
Our team has also prepared a short video for you. It will help you get the idea of how you can create rooms of any shape you need: