Assigning drive letters in Windows 10

I am running Parallels 12 on an iMac (Sierra). I am having trouble controlling the drive letters assigned to file system on my iMac.

I need to ensure that two particular file systems have the same drive letter every time that I run Parallels. But, when I run Parallels, the drive letters assigned vary based on which file systems are active on my iMac (e.g. do I have temporary USB drives connected or not). I have reviewed the Knowledge Base on this topic but the only article relates to Windows 7 and is not relevant for my Windows 10. I have tried to access the drive map utilities but they don't seem to be active for the mapped iMac drives. And, none of the mapped drives show up when I go the Windows 'drive management' utility. And, none of the Parallels configuration options seem to relate to this. If I could specify to Parallels which drives to map, that could help the situation but that doesn't seem to be under my control as far as I can see.

Any advice appreciated.

 

OK, answering my own question. Here is process that works for me.
I want to share only selected drives/folders from my iMac to my Windows 10 software when running Parallels. After experimentation, the following process works.
Step 1: Parallels Configuration
1. Open the Parallels configuration option box. This can be found from the icon at the top of the iMac screen or in the gear wheel at the top of the Parallels window.
2. Go to the 'Options' tab and open the 'Sharing' section.
3. Remove the check-mark for the 'SmartMount' option (Map Mac Volumes to Windows). This prevents Parallels from mapping all open Mac volumes to drive letters. I can then select only the ones the I want mapped.
4. Click the 'Custom Folders ....' Button under the 'Share Folders' section.
5. Add each folder/drive that you want to share with Windows. They can each be assigned a drive letter.
6. Click 'OK' and close the configuration box.
Step 2: Set the Windows drive letters
1. Open Windows Explorer
2. Click on 'This PC'. This will bregin up a ribbon display at the top of the window. If this isn't seen, click on the 'downward pointing arrow' in the upper right corner of the explorer window (beside the 'help' question-mark icon).
3. Click on the 'Map network drive ...' option.
4. Use this to assign drive letters to the folders added above.

a. Select the drive letter.
b. Click on 'Browse'.
c. Open the 'Mac' option in the box which opens.
d. Click on the file system/folder that you want to link to the drive letter.
e. Click on 'OK'
f. Make sure the 'reconnect at sign-in' box is checked.
g. Click the 'Finish' box.​

When you re-boot the Parallels software, the required links should show in the Explorer window.
In my case, I also have the 'home' drive mapped to 'Y:' and 'all files' mapped to 'Z:'. These aren't needed but I decided it wasn't worth figuring out how to prevent them from being assigned a drive letter.