After unfortunately not making any progress with Stardock support on my changing screens / docking stations issue with Windows 10 (linked above), I have switched to StartIsBack which provides the option to center my icons and works fine when I connect/disconnect and is in active development. It of course lacks all the features of Start11 but I really wanted the centered icons given I use a widescreen monitor size.
I did have similar issues with TaskbarX so appreciate the challenge in getting this right. For now, I am least able to get what I want working. I hope to return to using Start11 when I upgrade to Windows 11 in the future.
All the best!