The maneuver is more complex because it lacks the option found on Linux derived from Ubuntu.
Prerequisite:
- An GPT scheme disk
- UEFI by default in the bios
To check if GPT => https://www.tenforums.com/tutorials/848 ... ndows.html
To change the disk scheme without data loss => https://docs.microsoft.com/en-us/window ... mbr-to-gpt
First step.
We need to install Linux Mint 20 to create the grub bootloader and the main partition, just follow a traditional installation, at the time of the type of installation choose the option install Linux Mint alongside Windows 10, then choose the allocated size for Mint.

The bootlader will be installed in the /boot/efi partition from windows 10 and an single partition for Mint are created.
Now we have the necessary base to install lmde, just create an bootable media with the LMDE iso. (Don't forget to verify your iso)
Second step.
Boot on the created media, arrived at the installation type menu choose the option "Something else":

After that we go into the LMDE partitioning menu, we will delete the partition created previously because it does not include any swap partition, select modify partitoons and an gparted window appears:


Now it's time to create the partitioning scheme, starting with the swap, by default the swap is equivalent to the size of the computer's onboard memory, just adapt according to your memory capacity, in my example 16G ram = 15,7G swap:

Then we create the root partition for the system files, in my example 30G size in ext4 format:

And finally the last partition, our home, with the remaining space as size in ext4 format:

Now let's apply partitioning:

After that we return to the initial partitioning menu, where we will choose the necessary mount points for partitions:
just made an right click on the second partiton after swap and choose the "/" for root, for the last right click then choose "/home".

Next step will install the grub bootloader, I left the default option:

Then we have the summary of our partitioning scheme:

To finalize just select Install and done!
Overview after lmde is installed alongside Windows 10:

The result at the boot menu:


The both OS start without any incident.