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Boot Linux Ubuntu using Windows Boot Manager in Legacy mode, is this possible?

It might sound a noob question from the title, but I’m pretty new into operating systems.
I have a laptop and I would like to run Ubuntu alongside Windows 7. Windows 7 is the default OS, and the laptop also has its recovery partition.

The hard drive has the following partitions:

  1. FAT32 EFI partition (64 MB)
  2. NTFS Recovery (10 GB)
  3. NTFS Windows 7 (220 GB)
  4. EXT4 Linux Ubuntu (60 GB) (this partition has been obtained by shrinking the Win 7 factory original partition)

The boot is set to “legacy” in the BIOS menu, and by default, it boots on partition 3.

Now, I installed Ubuntu 18.04.4 LTS on partition 4, however, I didn’t install any boot manager because I don’t want to override the Master Boot Record as I’m not aware (at the moment) whether this will put me in trouble the day I want to do a factory reset using the laptop recovery tools.

Instead, my idea was to use bcdedit.exe to add a new entry to the Windows Boot Manager and make that new entry point to the Linux boot binaries. And here the problem, I cannot find anything on the internet that explain how to do that, so now I’m starting to think that what I want to do is not possible.

There is also the UEFI option, I know, but for the moment that way looks harder to me since the system was originally set to legacy, and if I just switch the menu to EFI and I reboot, Windows doesn’t load. Hence, taking this way means first of all study and understand EFI, then study and understand how to configure it to run Win 7, and finally run Linux. And understand if that switch allows me a factory reset if needed.

Question: can I boot Linux using my legacy boot mode and Windows Boot Manager, or it is simply impossible?

Thanks a lot.