Resolved Need help to install Windows in a MP 6.1

[Riwam]

I hope to find a kind soul to help me reinstall Windows 10 in my MacPro late 2013.
I had it already but I updated the MacOSX volume to High Sierra.
To keep my files I did not make a clean install but just upgraded it and it seemed to me to work OK.
For unknown reasons my Bootcamp Windows 10 got some time later corrupted.
I do not see any relationship to the upgrading of MacOSX.
It just happened some weeks later.
**** HAPPENS as they say.
To cope with such an eventuality I had made previously with Winclone (the only tool I know) clones of Windows, both "clone drives" and "images" in the Winclone file system.
However my experience with Winclone has not been a good and reliable one.
When trying to restore Windows it remains at the end with an eternal "updating legacy" and does not finish the restore.
The result is an unfinished, non booting, non working, useless "Half-Windows" partition to delete.
To reinstall it I have tried:
A) a DVD with a Windows 10 iso,
B) an image ESD.iso (without DVD),
C) an USB stick with Windows 10.
I tried to boot the Mac from external USB drives with versions of MacOSX previous to High Sierra, each with its own Bootcamp Assistant:
1) Sierra
2) El Capitan
3) Yosemite (this one requires an USB pen drive).
It all begins normally but...
...after downloading the Windows Support software from Apple and setting the size of the Bootcamp Partition, the Windows install procedure does not work as it should.
For unknown reasons and for purposes which elude me, besides the 2 partitions of the inner SSD (for MacOSX and for Bootcamp), many more small partitions are created which I do not dare delete!
(AFAIK one called something like OSX-Reserved contains the downloaded drivers, but what the others are is to me a mystery...)
When I choose the one which in size corresponds (almost) to what I had allocated for Bootcamp Windows ("almost" because of the many small partitions mentioned) the set up gets stuck.
The Windows installer tells me that
"it could not create any new or find any existing partition"
suitable to go on.
I deleted the chosen partition, created one again in the unallocated space and formatted it.
This many many times again and again.
Still I find no way to convince the installer that any partition is suitable to install Windows 10 in it.
I do not know what I am doing wrong and would appreciate very much any kind help.
Thank you very much in advance!!!
Ed

 

[Weaselboy]

Can you boot to Internet recovery (command-option-r boot) then use Disk Util to resize the main volume back to one large volume? Then boot back to macOS and use Bootcamp assistant to make a new Windows partition and install Windows?

 

[Riwam]

Can you boot to Internet recovery (command-option-r boot) then use Disk Util to resize the main volume back to one large volume? Then boot back to macOS and use Bootcamp assistant to make a new Windows partition and install Windows?

Thank you very much Weaselboy for your answer!
My inner SSD HD is already in one Mac High Sierra Volume.
I booted from a clone, erased it and with CCC cloned it back.
For reasons I do not understand it takes now more time to boot than before the whole unlucky efforts but it works and is in one piece.
My problem is what to do now.
The BootCamp Assistant will again probably create me more than ten small partitions and I am very much afraid that after the download of the drivers and the restart to begin the Windows set up I will again receive the message the set up could not create or find the suitable partition for Windows.
I had a very difficult time and wasted my poor nerfs with that I would like to avoid repeeting.
To do so I must understand why no partition was acceptable... Could SIP had something to do in your opinion or not at all? (With Yosemite it did not work either!)
Thank you again for your good will I appreciate very much!!!!!!!

 

[Weaselboy]

Could SIP had something to do in your opinion or not at all?

I don't think SIP would impact this, but I have not used Bootcamp is quite a while, so you may be right.

 

[Riwam]

I don't think SIP would impact this, but I have not used Bootcamp is quite a while, so you may be right.

Thank you again for trying to help me.
If you hear or read something which might explain why my predicament takes place or how to bypass it, please let me know.
Have a nice evening and a very good week!
Ed

 

[Riwam]

I don't think SIP would impact this, but I have not used Bootcamp is quite a while, so you may be right.

Unfortunately disabling SIP brought no improvement.
The problem appears when Windows restats and searches a partition to begin the set up.
For reasons I do not understand no partition among those present is considered suitable! Why not?
Still hoping for a good soul showing me the explanation... what am I doing wrong?
It must be something logical, am I right or wrong?
Ed

 

[Riwam]

Not knowing what to do and where to find help, I dared contact Apple Support (although my Apple Care finished long ago) ...and even if BootCamp has to do with Microsoft Windows... a very friendly technician named Christian and situated in Rostock (north Germany) phoned me back.
He spent at least an hour (long distance international call to Basel in Switzerland!!!) with incredible patience and goodwill only Apple in my experience is nowadays able to show!.
He made me download in Safari a special software which allowed him to see my desktop as if he were sitting by my side.
Somehow after a couple of reboots and (unexplainable possible) changes in the partitioning of the only inner SSD of my MP 6.1, it began magically in the second trying the set up of Windows 10 from an .iso I had previously downloaded.
Why it worked now and why it did not before remains an unsolved mystery ... but the point is I have now a working Windows 10 taking one third of my inner SSD, the rest remaining High Sierra.
Some things actually "changed" after the second rebooting the technician had me done, like the name (number) given in disk Utility to the created disk, which was the partition for Windows which finally was accepted by Windows for the set-up.
Also the sudden appearance of the OSX_RESERV 7.5 GB sized partition including the drivers previously downloaded by BootCamp before formatting, among the list of Disk Utility partitions.
I do not actually care to understand the whole matter and anyhow my skills are far from being able to do so.
The result is the one I wanted and that is enough for me.
I have however now 2 (TWO) entries in the Option Key Start-Up manager labeled both "Windows" .
If someone knows how to configurate the start-up manager to remove the second "Windows" option (which leads to a renewed Windows installation if clicked on it) I will be glad to learn where the start-up manager of a mac sits and how to correct it.
If not, I can live with an unnecessary second Windows option when booting my mac with the option key.
To end this story my great respect and admiration to Apple's Support and to its technicians who show so much patience and goodwill for a long ago sold computer which has not even any longer Apple Care!!!
For me once Apple - forever Apple!
Ed