How do I repair BCD error 0xc0000225 in a triple booted system?

I've got a triple booted system from my great-aunt to repair: It has:

1. Win7 x86 Pro
2. Win10 x64 Home
3. Win7 x64 Ult

Each is on 3 different partitions on an SSD disk, in that order. This used to work, but not now, as I accidentally deleted the Win10 partition and despite my best efforts to undelete it... no joy.

• When I boot to Win10, it gives BCD not found error 0xc0000225, while the other two boot up without problems. What makes this a little different is that the boot menu was that of Windows 7 before install, not the blue fancy graphic one we see in Win8 and Win10; almost like Win10 wasn't "boss". What speaks against this is whenever booted to Win10, it resided on C:, relegating Win7 x32 to B:, whereas when booted to Win7 x86 or x64, it resided on C:, relegating Win10 to D: and Win7 x64 to E:.

I've tried the following with no result, Win10 didn't boot up, and the other two booted up normally
(system restore isn't possible, there were no SR points made).

1. Windows Automatic Repair

2. Rebuild the BCD (at the Command Prompt I ran):

   bootrec /scanos
   bootrec /fixmbr
   bootrec /fixboot
   bootrec /rebuildbcd
   

3. I set the Win10 to active Partition with Diskpart using these commands:

   diskpart
   list disk
   select disk 0
   list partition
   select partition 1
   active
   

This resulted in the system not booting at all anymore, going straight to
BCD failed to start error 0xc00000f

edit: 4. I forgot to say, I used a gui BCD editor (which I can't mention the name of for religious reasons), but it didn't help.

I've used a Win10 ISO USB to reboot the laptop (Lenovo Z50-70) to get into the Repair Mode, and I'm in the unfortunate position that my great-uncle, whose machine it was, isn't around to ask him questions about this machine.

Question: What else can I try to repair this?

I don't consider format+reinstall and similar solutions a repair, I'm sorry about that.

I've found the error, which was as if often is, rather simple to correct... on hindsight. Using the previously mentioned gui BCD editor, (which can't be named for site religious reasons), I saw upon closer inspection that the Windows 10 bootup, didn't point to any partition. So, duh, of course it gave a "not found" error.

Since I couldn't detect an edit option for the different entries, the quick-&-dirty solution was to add a fourth entry, make it point to my "D"-station and delete the faulty one.

No complicated bcd editing was required.

I apologize for not saving screenshots.

EDIT: Upon closer inspection, one can use the fourth option called "Advanced Settings" in the previously mentioned gui BCD editor to indeed, edit the entries. Quite simply too. Oops.