pattern - The Case of the Missing Rebus

A rebus has gone missing.   What rebus, and under which $~\boxed{\sf~ \raise{.5ex}\underline\quad \, ? ~\raise{.1ex}\strut}$ ?

$$ \color{#274}{\boxed{ \quad \begin{matrix} \\[-1ex] & \kern-1em \rm ADAD & & \raise{2.5ex}\strut \kern-2em\raise{1.2ex}\color{black}{\boxed{\sf~ here? ~\raise{.1ex}\strut}} \\[-1ex] & \kern-1em \rm ADAD & & & & \kern-1em\rm LLL \\[-1ex] & & & & & \kern-1em\rm LLL & & \kern-1em x \, y \\[-1ex] & & & & & & & \kern-1em z \:\: t \\[-1ex] \rm XCXC & & & & & & & \\[-1ex] \rm XCXC & & & & & & & & & \kern-2em\raise{-2ex}\color{black}{\boxed{\sf~ perhaps? ~\raise{.1ex}\strut\raise{-.2ex}\strut}} \\[-1ex] & & \kern-2em\raise{1.4ex}\color{black}{\boxed{\sf~ maybe? ~\raise{.1ex}\strut\raise{-.2ex}\strut}} & & \kern-1em\rm TTT & & \\[-1ex] & & & & \kern-1em\rm TTT & & \kern-1em\raise{-1.2ex}\color{black}{\boxed{\sf~ or? ~\raise{.1ex}\strut}} \\[-1ex] & & & & & & & & & & & \kern-1em\rm Sn \\[-1ex] & & & & & & & &\kern-1em ~ 2e/6 & & & \kern-1em\rm Sn \\[0ex] & & & & & & & &\kern-1em e/2 {-} \!\; e/6 & & \\[-1ex] & & & & & & & & & & \kern-1em\rm TT \\[-1ex] & & & & & & & & & & & & \kern-1em\rm ZZZZZ \\[-1ex] & & & & & & & & \raise{-1.7ex}\strut & & & & \kern-1em\rm ZZZZZ \\ \end{matrix} \quad }} $$

Naturally, the answer may be rebused more than one way.

Nothing is under three of the $~\raise{-1.2ex}{^{^\boxed{\sf~ \raise{.5ex}\underline\quad \, ? ~\raise{.1ex}\strut}}}~\!$s.   Hint from a comment:

The clues $\rm\raise{-.3ex}{\color{#274}{~ \atop TT}}$ and $\rm\raise{2.3ex}{\color{#274}{\raise{-.5ex}{Sn} \atop Sn}}$ lead to stereotypical New Zealand pronunciations.

Answer

The missing rebus is:

TTT T TTT or anything else that gives seventies

And it needs to be positioned under the box labelled:

maybe?

---

Reasoning:

Reading from left to right, ignoring vertical position, we have:

XCXC XCXC - XC is Roman numeral for 90, and there's multiple, so we've got nineties
ADAD ADAD - a plurality of ADs or eighties
...the missing one needs to go in here...
TTT TTT - six Ts, or sixties
LLL LLL - similarly with Roman numeral 50s gives fifties
xy z t - the four dimensions, or 4Ds, giving forties
2e/6 e/2−e/6 - both equations resolve to a third of e, but there's two, so we get third es or thirties
TT - twin Ts, or (again with an NZ accent) twenties
Sn Sn - Sn is the chemical symbol for Tin, and we've got more than one, giving us Tins, or (putting on our NZ accent) tens
ZZZZZ ZZZZZ - we've got two rows of Zs, or Z rows, giving zeroes

However, the above solution leaves two possible positions that the missing rebus could appear in:

maybe? or here?

But, if we consider the derebussed words in order of height in the graph, we get:

here?
eighties
fifties
forties
nineties
maybe?
sixties

tens
thirties
twenties
zeroes

It should be painfully obvious, even to the most dimwitted of individuals*, that the words are in alphabetical order... Thus seventies, must be hidden under maybe? to complete the pattern.

_{* I stared at the list for quite some time before realising}