SOLVED! I think at least 99% solved.
I will post the results here so that it is on record for future reference should someone else encounters similar and hopefully it will be helpful.
First, I would like to thank you dmt for your time and attention with my cloning process; Nachlese for your added input; and Trimoon for your reminders 
I will described in summary (no great details) the results after my “dd” cloning operation (even though not recommended by fellow forum member, dmt) plus trying to fix lots of errors with booting and ending up installing over the cloned partition /root on the external SSD as well.
Disclaimer: For those who are looking to do similar, you may want to try copying over your desired portions/features or other methods instead of using “dd” since the latter method hadn’t shown me to be working as smoothly as I had intended but it certainly gave me, as a Linux novice the opportunity to learn from “real time” (yes, many many hours of it) lessons.
- “dd” cloned from laptop (dual-booting Manjaro linux and Windows10) two partitions /root and /home over to the external SSD (single-booting Fedora linux). Straight-forward success.
However, boot-loader issues presented lots of conflicts that I did not initially understand because it involved device UUIDs also cloned over to the external SSD, thus confusing the whole thing from working and booting properly.
- Went against “warnings” to not edit those config files, I went ahead and mucked around on both systems with fstab files, xorg.conf files and grub.cfg files and saw more errors but I did learn a lot more through trying to fix those errors. Precious lessons
Some successes which led to more understanding of how somethings work under the “hood”.
Important step.
Had realised that the cloning process brought over same UUIDs to the external SSD, so regenerated new UUIDs for the devices /root and /home.
- Despite fiddling around with all those config files and still experiencing a lot of errors, the most straight-forward and simple thing that helped in the end was to have found the answer to the booting issues at GRUB/Restore the GRUB Bootloader - Manjaro.
Launched into the Manjaro “live USB” environment to execute the above process for the laptop as well as the external SSD. That fixed the loading of Manjaro on the laptop but not for the external SSD as the boot loader on the external SSD still pointed to the /root on the laptop.
I decided to reinstall Manjaro on the external SSD to see if it would sort out the connection to the laptop.
- Fresh-install Manjaro onto the external SSD (1TB).
Using Gparted as partition manager, I resized the /root (45GB) and /home (80GB). Retained the /boot (1GB) partition and created a /swap (8GB) partition.
From the “live USB”, I installed over the existing /root partition on the external SSD. It went smoothly.
Surprise.
Somehow, instead of installing a fresh Manjaro onto the external SSD /root, I found out that all of the cloned features from the laptop including internet, bluetooth, etc. settings also got retained in the new installation. I did not know how but glad that perhaps the Manjaro installation process had taken into consideration the existing OS and only “updated” the Manjaro rather than completely “overwritten” it. This part I have not understood yet.
- Finally, both the boot loaders on the laptop and the external SSD are working independently and correctly targetting the respective /root partitions EXCEPT that somehow the external SSD still maintained the entry for Windows10 which did not exist on the external SSD.
I went inside the grub.cfg file to remove the entry for Windows10 and now it all works well, both the external SSD installation and the existing laptop system.
- The one issue that still isn’t resolved is on the laptop initial loading process where it is still flashing the error:
Failed to start. Remount root and kernel systems
The system still loads and work normally but I am still finding out how to remove that error message.
That’s all for now.
Cheers and thanks again for your help.