Thanks for your solutions 
Tried "copy-"solution “shim.efi” to “bootx64.efi” -> Entry boots opensuse but error still consists
/boot/efi/EFI/boot # ls -la
drwxr-xr-x 2 root root 4096 Feb 19 17:18 .
drwxr-xr-x 4 root root 4096 Feb 19 17:12 ..
-rwxr-xr-x 1 root root 1263312 Feb 14 15:21 MokManager.efi
-rwxr-xr-x 1 root root 1336112 Feb 14 15:21 bootx64.efi
-rwxr-xr-x 1 root root 1336112 Feb 14 15:21 bootx64.org.efi
-rwxr-xr-x 1 root root 1209656 Feb 14 15:21 fallback.efi
-rwxr-xr-x 1 root root 120 Feb 14 15:21 grub.cfg
-rwxr-xr-x 1 root root 1197936 Feb 14 15:21 grub.efi
-rwxr-xr-x 1 root root 139264 Feb 14 15:21 grubx64.efi
efibootmgr -c -L "Windows Boot Manager" -l '\EFI\boot\bootx64.efi'
efibootmgr -c -L "opensuse-secureboot" -l '\EFI\opensuse\shim.efi'
efibootmgr -o 0000,0002,0001
efibootmgr -n 0000
efibootmgr -v
BootNext: 0000
BootCurrent: 0000
Timeout: 0 seconds
BootOrder: 0000,0002,0001
Boot0000* Windows Boot Manager HD(1,GPT,9d96a519-6ad4-4cbb-9ce0-b92ed0148b94,0x800,0x100000)/File(\EFI\boot\bootx64.efi)
Boot0001* opensuse HD(1,GPT,9d96a519-6ad4-4cbb-9ce0-b92ed0148b94,0x800,0x100000)/File(\EFI\opensuse\grubx64.efi)
Boot0002* opensuse-secureboot HD(1,GPT,9d96a519-6ad4-4cbb-9ce0-b92ed0148b94,0x800,0x100000)/File(\EFI\opensuse\shim.efi)
Tried “Microsoft”-solution “shim.efi” to “bootmgr.efi” labeled “Windows Boot Manager” → Entry boots opensuse but error still consists
/boot/efi/EFI # ls -la ./Microsoft/Boot/
drwxr-xr-x 2 root root 4096 Feb 19 17:48 .
drwxr-xr-x 3 root root 4096 Feb 19 17:38 ..
-rwxr-xr-x 1 root root 1336112 Feb 14 15:21 bootmgr.efi
-rwxr-xr-x 1 root root 120 Feb 19 17:44 grub.cfg
-rwxr-xr-x 1 root root 1197936 Feb 19 17:44 grub.efi
efibootmgr -c -L "Windows Boot Manager" -l '\EFI\Microsoft\Boot\bootmgr.efi'
Tried coping whole directory opensuse to boot → Entry boots opensuse but error still consists
/boot/efi/EFI # mv ./boot ./boot.org
/boot/efi/EFI # cp -av ./opensuse ./boot
all ended up in the original problem.
FAT32 / FAT16 - solution
Do i need to to reformat ?
lsblk --output NAME,LABEL,MOUNTPOINT,UUID,size,FSTYPE
NAME LABEL MOUNTPOINT UUID SIZE FSTYPE
sda 931.5G
├─sda1 efi /boot/efi 1189-08BB 512M vfat
[FONT=monospace]├─sda2 boot /boot ea854f0e-8ff2-42b9-8478-9285c0ddf4bd 1G ext4
[/FONT]
cat /boot/efi/EFI/opensuse/grub.cfg
search --fs-uuid --set=root ea854f0e-8ff2-42b9-8478-9285c0ddf4bd
set prefix=(${root})/grub2
source "${prefix}/grub.cfg"
If there is no need to reformat, then i will test “rEFInd” - solution…
For Information only:
Figured out, if i do not boot the original “shim.efi” (EFI\opensuse\shim.efi), i am not able to write boot entries or boot order with efibootmgr
efibootmgr - Could not prepare Boot variable: No space left on device