Multi Boot system Easy BCD issue

Post a screen shot of Disk Management then we'll go from there:
Screenshot - Take in Windows 10 - Windows 10 Forums

When you install Linux, the best way is to disconnect everything including the M.2 so that it will create its own grub loader. Since you did not disconnect the M.2 SSD, Linux override Windows Boot Loader with Grub. You'd need to reformat the System Reserved Partition to get rid of grub loader.
Boot into WinRe, open Command prompt and type:
diskpart
select disk 3
select partition 1
delete partition override
create partition primary
format quick fs=ntfs Label="System Reserved"
assign letter=W
active
exit
bcdboot C:\Windows /s W: /f BIOS

The procedure above will rebuild the Windows Boot Manager with single boot into Windows Pro.
reboot the PC then use Easy BCD to add other Windows (7/8/10) for mutiboot

NOTE: You won't be able to add LINUX using Easy BCD. You'd need to delete the LINUX partition(s), disconnect all other Drives including M.2, re-install LINUX then use Easy BCD to add it to multiboot.

The screen shot below demonstrates how it works:
#1 Single Windows installed
#2 Linux installed with Windows disk(s) connected. This is how your current Windows/Linux setup
#3 Install Linux without any Windows disk(s) connected so that it will have its own Grub boot loader then use Easy BCD to add Linux to Windows Boot loader. This is the preferred option so that any subsequent Windows/Linux Updates will not interfere with each others.