I made a quick check at Majorgeeks and found several programs including freeware versions to adjust drive partitions.I haven't used any of these so I cannot provide any recommendations. One product "EASEUS" indicated that it could re-establish a deleted partition and files in deleted partitions. That capability could prove vital in your desired task.

With this type software you can adjust existing partitions and create new ones.

Another solution would be to install another drive in your computer for the second OS. That is the method I used the last time I had two OS's on the same computer.