Defraggler reports W10 Storage space as an SSD, hence I cannot defragment it.
Windows 10 'Storage Spaces' are neither SSD or HDD. (or could be both, depending on how you want to look at it).
They are logical/virtual drives that are 'pooled' across several physical drives.
The physical drives in the 'pool' could be a mix of different types of drive, and of different formats - so because of that the 'Storage Space' cannot normally be defragmented.
https://www.dummies.com/computers/operating-systems/windows-10/working-windows-10-storage-spaces/
A fairly comprensive guide to Win10 Storage spaces: