The little lamed was serving as a reminder-flag, telling you to recall other, relevant, words beginning with lamed. The little ayin had to do with numerical symbolism.
The little tet had numerical symbolism and reminder-flagging, all of it connected to the destruction of the Temple in various ways.
That recap over, let's move to Kohelet, pictured here in a festive green wrapping (you recall Eicha was wrapped in bodacious black...Megillot are fun like this, you can dress them up in seasonal clothes).
Eicha, if you remember, had a lot of white space. Kohelet has barely any. There's one break right at the beginning, a good deal in the Song of Times (I'll do a picture of that later), and then it's just a Text Wall of...well, I was going to use internet parlance and say a Text Wall of Doom, but it's not really Doom. A Text Wall of Gloom, perhaps? A Text Wall of Gloom Tempered With Hedonistic Pragmatism?
We digress. The point is that Kohelet has basically no section breaks; one at the beginning, none in the middle, and none at the end either.
What it does have, at the end, is a Big Tet.
(The writing's not great. I was rushing rather, to get it finished before yom tov - I only had ten days, and it's not a short book.)
So, the big tet? Quite possibly just a way of saying "New section, chaps!"
But that's far too prosaic.
Back to Tzvi Ron and his Sefer Katan v-Gadol (and G. Wasserman's translation).
The Big Tet is in the phrase טוב שם משמן טוב - a Good name is better than good oil.
The Rokeiach (חסידי אשכנז) says: טוב שם משמן טוב -- the tet is large, because a good name has a LOT of good.
There's another large tet in Tanakh, in Job: יסר מעלי שבטו- "Let him take his rod away from me."
Job is complaining about his great suffering, being beaten by God's staff. מסורת הברית הגדול, section 1518, says that that big tet links to our big tet here in Kohelet, and demonstrates that suffering is ultimately good.
On the other hand, Rav Dovid Tevele (17th- or early 18th-century Hamburg) says that the large tet in טוב שם משמן טוב is a hyperlink to the small tet in Ekha, טבעו בארץ שעריה, with a popup from the Midrash.
Remember the bit when Tamar was going to be burned for whoring around?
According to the Targum Yerushalmi, she lost Judah's pledge (his seal and staff and cord), and she prayed to God to let her find it, and thus rescue herself from being burnt, so that she might ultimately be the ancestor of three tzaddikim who would be untouched by fire - namely, Hananiah, Mishael, and Azariah, from the book of Daniel.
According to Shemot Rabba 48:1, our verse טוב שם משמן טוב -- a good name is better than good oil -- means that the "good name" of Hananiah, Mishael, and Azariah was better than the "good oil" with which Nadav and Avihu were anointed, when they first became priests.
So, R' Tevele comments:
When the temple was destroyed (טבעו בארץ שעריה, with a small tet) and the anointing-oil of the priests was no more -- nevertheless, in that cold exile, three tzaddikim arose, Hananiah, Mishael, and Azariah, and their good name (large tet) overwhelmed the destruction of the temple (small tet).
So, God paid us back for the loss of the Temple, by giving us tzaddikim, who were even greater. And hopefully, in the merit of further tzaddikim like them, נזכה למלך המשיח ויעלה השערים הנטבע בעו"ה ויקים סוכת דוד הנופלת במהרה אמן, may God send the Messiah, who will bring up the gates of the Temple, which had sunk (טבעו, with small tet) deep into the ground, at the time of the Destruction.