Well dear unRaid community; I solved my problem and it is something no one thought of telling me.
It is time for me to swallow my pride, tell everyone of my stupidity an contribute one more fix to the dreaded '0x80070035 error':
Solution:
Microsoft does not find a drive if it is set as INVISIBLE on your unRaid share.
Go to your unRaid setup page, under the share tab look for the setting 'Export' and read the description. Set it up to 'Yes'.
Thank you for your guidance, Frank1940, and to the unRaid community across multiple platforms (fb, reddit, youtube) for answering my stubborn and incessant questions. At least I gained quite an understanding of a lot of inner workings for this software.
Do not hesitate to PM me to ask for assistance.