Grub2Win VS Lilo

Use https://sourceforge.net/projects/grub2win/ to manage dual (multiboot) from Windows , makes yput life easyer. If you have more than one disk instal Linux on a separate one if not you need to create a separate partition. When you install Linux if you have 2 drives make sure that Linux grub (bootloader) is installed on the drive wher Linux resides, not on the one where Windows and it's bootloader is, in case you... Source: about 1 year ago

Otherwise, what you'll have to do is image a USB drive with a partition management software or distro (e.g. GParted Live), boot from it, and then resize your partition from there. This does carry more risk of data loss than the dual SSD method, but it's more universal (you haven't mentioned if this is a laptop with more than one removable storage option or not, for instance), and it's unlikely to cause any harm.... Source: over 1 year ago

I have a suggestion, follow the previously advised installation process to install CrOS Flex on a separate drive, then reconnect and enable the Windows disk through the boot menu, once back there you can install a GRUB manager under Windows, like Grun2Win, it's easy to install and set up, once you are all done, the final result will be easier to switch from one OS to the next, instead of every time going through... Source: almost 2 years ago

When using Opencore for booting Windows 10, causes many issues. Even it causes issues when you boot MacOS after restarting from Windows 10. So Fix is Simple Use Grub2win as main bootloader and boot Windows or Opencore ( Chainload opencore efi file) from there. I am available for your queries and help. Source: over 2 years ago

However, I have used this https://sourceforge.net/projects/grub2win/ I install it on the windows side and configure it. It will enable me to choose ubuntu> Ater booting in Ubuntu, I do grub install. If that's too complicated to install grub repair when you boot into Ubuntu and run it. Source: almost 3 years ago

Goodeed is in no way affiliated with Ecosia but I find it relevant to put it because it has a similar ideology to ecosia or Lilo. Source: over 2 years ago