I'd like to understand this more Andabien, what type of things/movements are you thinking of? Like varying height, energy, quality, rotation, foot placement, embrace?
Yes, to all of the above. I'll try, but for me, the closer we get to discussing essential tango, the less able we are to express it verbally.
Comparing tango to painting
There are only three primary colors. Add to that the three secondary colors. Add to that all the intermediate qualities of hue. Add also the qualities of saturation and shade. Then include the blends from one color to another. Add also the qualities of stroke: strong to light, bold to timid, big to small, straight versus meandering, etcetera. But, painting has no temporal dimension, as dance does.
Comparing tango to music
There are only 12 notes in the western scale. Every note also has duration, attack, release, crescendo, decrescendo, loudness and softness, vibrato, phrasing, etcetera. No good musician would play music exactly as written, because the written music cannot describe the real music.
Dance
For me, it's similar in tango. If one only thinks in terms of the elemental steps, of which I define six for the followers (forward, backward, sideward, ocho in front, ocho in back, cruzada), plus combinations of those steps, I think you miss out on all the other qualities that cannot be described, but can be danced: strength or softness, boldness or uncertainty, size, tempo, repetition, contrast, emotion, etcetera and etcetera.
For me, tango goes way beyond paint by numbers. It goes way beyond merely playing the notes as written. It goes to a realm that can be expressed and experienced, but cannot be described or enumerated. If you can talk about it, it's not the real dance.
Feeble as it is, I hope that helps.