I have a FlexBook13 with two physical drives:
My problem is that there is not enough space on Disk 1 (28GB) to install all Windows 10 updates.
I've tried to install other programs on D drive, but it didn't help. There is not enough space. Disk 1 has 3 factory set up partitions (C -the main system and two other for the recovery purposes).
Is it possible to make Disk 0 (currently mapped as D drive) to become C, and visible as the boot partition? Is it possible to i.e merge the two physical drives to be visible as one single C drive?

%UserProfile%\Documents,%UserProfile%\Downloads, etc.) to a different drive via each directory's Directory Properties > Location tab > enter new path > OK. There's 13 user data directories that can be moved, however the%UserProfile%\OneDrivedirectory will need to be moved via the OneDrive application (you may have to sign out of the OneDrive application, then re-configure it manually to store the OneDrive directory on a different drive). – JW0914 Jan 01 '20 at 13:25