Parallel? How do you set the VTA?

Every cartridge I have requires a different vta to sound best and, as Raul mentioned, records are all different in thickness which changes the vta.
Dougdeacon is the only other post that makes any sense to me because first, most tables are not 'dead nuts' level so using a bubble only compounds the error. Bubble levels are not very accurate to begin with. Parallel to the record surface is a starting point and we can all get there by eye quicker than with levels, cards, graphs etc. From there it becomes listening by trial and error to find the sweet spot.

Actusreus-
You said in op "silly question", I want to agree with you.

You asked "how to detirmine conclusively if arm is parallel"
VTA is a "moving target" that changes everytime you change records.

So, it can't be detirmined conclusively.

Therefore, charts, levels, cards etc. seem like a waste of time/effort to me or "doesn't make sense to me"

Nothing personal, I was just sharing my experience with vta.

Brf-
How does this paradigm deal with the different thickness of records? Within each record the stylus will rise and drop, how should we account for this change in sra?

We will never agree on a solution until we agree on what the target is. More complicating, a moving target everytime we change records.

Thanks for all the good ideas. I have to admit that after initial set-up I only change vta when something doesn't sound right. The arm on the Traveler is very easy to adjust on the fly but I never seem to change unless something is wrong. I listen to albums that I am very familiar with every day or two, it lets me know if things are dialed in to my liking.
At least we all agree that when it's right we can tell because nothing makes that music sound as good as stylus on vinyl.