Here is how to increase disk space on Hyper-V platform for NSM On-Prem virtual machine.
Step 1: Shut down the NSM VM;
Step 2: Expand the virtual Disk (VHDX)
Open Hyper-V Manager:
Right-click on the VM and select Settings.

Under Hardware, select the Hard Drive you want to expand.
Click on Edit (next to virtual disk path).
The Edit Virtual Hard Disk Wizard will open. Click Next.

Choose Expand and click Next.

Specify the new disk size (here increase to 450GB).

Click Finish.

Now boot NSM On-Prem VM, noticing the Disk Space expanded:
