how to triple boot by adding 3rd SSD drive with Mojave?

[MPG951]

I currently have Sierra + Windows on separate SSD drives since 2016. What would be the process for installing Mojave on a third internal SSD. I tried installing mojave to an external SSD but I could not finish the install process as the bootloader does not show the Mojave SSD after restarting even though it seemed to be installing and I believe the EFI for the Mojave SSD is empty after mounting it on Sierra. Tried this method on other macbook and mojave installed on the external SSD & booted. What gives.

 

[P1LGRIM]

Moved to Multi Booting.

 

[Going Bald]

I currently have Sierra + Windows on separate SSD drives since 2016. What would be the process for installing Mojave on a third internal SSD. I tried installing mojave to an external SSD but I could not finish the install process as the bootloader does not show the Mojave SSD after restarting even though it seemed to be installing and I believe the EFI for the Mojave SSD is empty after mounting it on Sierra. Tried this method on other macbook and mojave installed on the external SSD & booted. What gives.

You are aware there are no drivers for your GPU in Mojave, yes?
To install Mojave on a 3rd SSD, disconnect the Sierra and Windows drives, connect new drive. Install Mojave per the forum guide for installing Mojave. Install Clover to Mojave drive and get it booting from the SSD without the install USB connected.
Boot to UEFI and make the Mojave drive first in BBS boot order. Note that Mojave will install APFS instead of HFS+ so the Sierra version of Clover will not boot it. I have never tried it, but you may find that the Mojave version will not boot the Sierra drive. You will just have to experiment for yourself.

 

[MPG951]

You are aware there are no drivers for your GPU in Mojave, yes?
To install Mojave on a 3rd SSD, disconnect the Sierra and Windows drives, connect new drive. Install Mojave per the forum guide for installing Mojave. Install Clover to Mojave drive and get it booting from the SSD without the install USB connected.
Boot to UEFI and make the Mojave drive first in BBS boot order. Note that Mojave will install APFS instead of HFS+ so the Sierra version of Clover will not boot it. I have never tried it, but you may find that the Mojave version will not boot the Sierra drive. You will just have to experiment for yourself.

I experiment with using a Samsung portable SSD T5 and I could not get intel hd graphics to be used. In the About Mac it showed only 7MB. Do you have any ideas how I can disable the NVidia GPU and use the integrated graphics. Also I decided to reinstall Mojave to the portable SSD after playing with the config.plist but the Mojave USB is not recognized so I can not boot from it any ideas what is the cause?