When creating a dual boot, you usually only need to create that partition for Windows 10 and the installation process automatically creates the boot loader so you can select which operating system to boot into.
I do not know what changes you made already with EasyBCD 2.4, but if you are using EasyBCD 2.4 to edit the Windows boot partition, you should be able to use that to remove the current boot configuration and add back the Windows 10 and 7 installations to the boot partition,