GG5, etc.

I think this gets the message across without going on about it.

@@ -11,0 +12 @@
+<ke_inf>&sK;</ke_inf>
@@ -14,0 +16 @@
+<ke_inf>&sK;</ke_inf>
@@ -24,4 +25,0 @@
-<k_ele>
-<keb>ガンクビそろえる</keb>
-<ke_inf>&sK;</ke_inf>
-</k_ele>
@@ -29,0 +28,4 @@
+</r_ele>
+<r_ele>
+<reb>ガンクビそろえる</reb>
+<re_inf>&sk;</re_inf>
@@ -37 +39 @@
-<gloss>to be gathered (lined up) as a group (e.g. officials at an apology press conference, or a group of bumbling subordinates, disliked peers, etc. )</gloss>
+<gloss>to sit silently (and submissively) at a meeting</gloss>

雁首揃えて	2698	49.3%
雁首そろえて	1975	36.1%
がん首そろえて	261	4.8%

ガン首揃えて	253
ガン首そろえて	148
ガンクビ揃えて	94
ガンクビそろえて	56


雁首を揃えて	294	5.4%
雁首をそろえて	187	3.4%
がん首をそろえて	24	0.4%

雁首を揃える
https://www.weblio.jp/content/雁首を揃える
人が集まり立ち並ぶさまを指す、やや口汚い表現。

雁首を揃える
https://www.waraerujd.com/雁首を揃える
people gathered together/lined up:
雁首を揃えるとは、勢揃いする、人が集まって整列するという意味の俗語的な言い方
Nuance: satire of useless people
「いい大人が雁首揃えてなにやってるんだ、役立たずめ」のように、「雁首を揃え」た人々を非難したり、皮肉ったりするときに使う。

http://yain.jp/i/雁首を揃える
人がその場に集まる、出揃う意味で、俗な言い方。


「雁首を揃える」とは？意味と使い方
A crowd of incompetent people (as one might see at an apology press conference 謝罪会見)
https://kotobaknow.com/gankubi-wo-soroeru
むしろ逆に、不祥事を起こした関係者の謝罪会見等で
整列して頭を下げている様子などを、
「雁首を揃えて頭を垂れる」のように表現します。

いずれにせよ「無能な者が群れ集まっている」といったように、
決して良い意味合いのものではないので、
あまり使用しないほうが、そして使用する機会も無い方が良い言葉です。

https://imidas.jp/idiom/detail/X-05-X-06-A-0006.html
何人かの人が首を垂れてかしこまっていたり、いっしょに行動したりするさまを、やや軽蔑（けいべつ）していう言葉。「いくらきみたちが雁首を揃えたって、課長一人の行動力にはとてもかなわない」
〔語源〕「雁首」は、もと、（雁の首の形に似ていることから）キセルの頭の、たばこを詰める部分の意。（それが人が首をうなだれているのに似ていることから）人の首・頭の意。

Here is an application where everyone is laughing(Abe and other politicians):
売国屋ども
雁首揃えて今こそ
島流しにせよ😠😠
https://twitter.com/NQlGID92gPGj6qb/status/1421092863790571523
It's the *people* and their (imputed) character that matter, not their demeanor specifically.

Among some not-so-useful example sentences, a good example
https://ja.ichacha.net/english/雁首.html
I know why you choose to have your little , ahem grouptherapy sessions in broad daylight .
真昼間に 雁首揃えて... 井戸端会議やるのも分かる

https://hinative.com/questions/19172947
「失敗をした部下たちが、雁首をそろえて謝りに来た。」・・・正しい使用例となります。

What is this guy saying?
https://www.romhacking.net/forum/index.php?topic=18235.0
The setup is that 2 females who fought for a country that was defeated are trying to join a new country. The king of the new country greets them with this. The king is supposed to be wacky and have an accent. The ガンクビ part is confusing me. I have a guess what it might be referring to but I don't want to get that wrong.  :-[

んーーー？　負け犬どもがガンクビ揃えて何の用だぁ？

ANSWER:
ガンクビ is slang for penis shaft, but I don't think that's what it means here. 雁首揃えて means "in a line," and I think the king is saying, "Hmmm? What are YOU losers doing here (lined up in front of me)?" Hope that helps. :)

=========
Decent image examples on twitter:
https://twitter.com/search?q="雁首揃えて"&src=typed_query&f=image

Started by reversing the xrefs.
Old gloss appears to be a fair ways off. I can sort of imagine how it might have been arrived at - maybe in the context of a large group of public officials who had gathered for a press conference, where one person spoke and the others sat by silently... But none of the terms "sit", "silent", or "meeting" (other than that some people have met) are part of the general implication of the expression. And it can't apply to one person, it applies to a whole group(*including* the speaker, in this press conference example). Suffice it to say, I do not think the old gloss should come back.

Pretty much all sources indicate that this is pejorative. 

Not used in the news or in "proper" polite speech, for obvious reasons, which seems to limit parallel translation resources.  I've found a few (refs).　Here's a good example in the wild:
いじめられっ子体質のチー牛が雁首揃えて何やってんだか. 

There's a song (which is where most google image hits come from) about a group of bullies. 
雁首、揃えてご機嫌よう (Subtitled in English)【ガチャクラブ/Gachaclub】
https://www.youtube.com/watch?v=kYix17mrTZc
Found an attempt at a title translation:
https://vocaloidlyrics.fandom.com/wiki/雁首、揃えてご機嫌よう_(Gankubi,_Soroete_Gokigen_you)
"雁首、揃えてご機嫌よう"
Romaji: Gankubi, Soroete Gokigen you
English: Line Up and Give Your Regards
(animated music video.  addressed to a group of school bullies who have made the protagonist's life miserable)
https://genius.com/Genius-english-translations-ukaroku-gankubi-soroete-gokigen-you-ft-hatsune-miku-english-translation-lyrics
NOTE: The xref with 顔 is probably not strictly synonymous-but-non-derogatory, but the meanings seem obviously related.  The xref is also missing nuance and needs some edits as well. (It's not "complete attendance", but "a complete assembly of all of the important/necessary people related to a task").

@@ -12,0 +13,15 @@
+<k_ele>
+<keb>ガン首揃える</keb>
+</k_ele>
+<k_ele>
+<keb>ガン首そろえる</keb>
+<ke_inf>&sK;</ke_inf>
+</k_ele>
+<k_ele>
+<keb>ガンクビ揃える</keb>
+<ke_inf>&sK;</ke_inf>
+</k_ele>
+<k_ele>
+<keb>ガンクビそろえる</keb>
+<ke_inf>&sK;</ke_inf>
+</k_ele>
@@ -19,2 +34,4 @@
-<xref type="see" seq="2073140">雁首を揃える</xref>
-<gloss>to sit silently at a meeting</gloss>
+<xref type="see" seq="1217580">雁首・がんくび・2</xref>
+<xref type="see" seq="2595960">顔を揃える・かおをそろえる</xref>
+<misc>&derog;</misc>
+<gloss>to be gathered (lined up) as a group (e.g. officials at an apology press conference, or a group of bumbling subordinates, disliked peers, etc. )</gloss>

@@ -19,0 +19,2 @@
+<xref type="see" seq="2073140">雁首を揃える</xref>
+<xref type="see" seq="2073140">雁首を揃える</xref>

Added additional PoS via batch update.Added additional PoS via batch update.
-*- via bulkupd.py -*-

@@ -18,0 +18,1 @@
+<pos>&v1;</pos>