If you don't want to mess with diskpart, you can do this in GParted. I tested this method on my machine and it works.

1. shrink /dev/sdb4 by 400MB (you've already done this)
2. unmount /dev/sdb2
3. copy /dev/sdb2 into the empty space between /dev/sdb4 and /dev/sdb5 (call this new partition /dev/sdb7)
4. enlarge /dev/sdb7 to take the entire 400 MB
5. delete /dev/sdb2
6. ensure /dev/sdb7 has the esp boot flag
7. if you use linux, update your fstab file to reflect the UUID of the new EFI partition

If you don't want to mess with diskpart, you can do this in GParted. I tested this method on my machine and it works.

1. shrink /dev/sdb4 (windows partition) by 400MB (you've already done this)
2. unmount /dev/sdb2 (efi partition)
3. copy /dev/sdb2 into the empty space between /dev/sdb4 (windows partition) and /dev/sdb5 (linux partition) and call this new partition /dev/sdb7
4. enlarge /dev/sdb7 (new efi partition) to take the entire 400 MB
5. delete /dev/sdb2 (old efi partition)
6. ensure /dev/sdb7 (new efi partition) has the esp boot flag
7. if you use linux, update your fstab file to reflect the UUID of the new EFI partition