Quorum and Organization Leaders Sitting Up Front

Just wondering, but should quorum/organization leaders sit up front in their respective meetings? I know this was commonplace a generation or two ago, but I don't see that as much anymore and I'm wondering if that was an actual church guideline or something that just kind of became customary.

After a quick scan of the General Handbook, I found 29.2.1.1 (item 3) pertaining to Sacrament Meetings:
"Presiding authorities and visiting high councilors should be invited to sit on the stand. General Officers are also invited to sit on the stand unless they are attending their home ward."

So at least for the Ward organization, presiding authorities are invited to sit on the stand [at the front of the congregation] during Sacrament Meeting.

I didn't see it immediately noted in the handbook/didn't search, but it's likely the same protocol for Stake Conference or other large meetings of Saints (Area Conference, General Conference, etc.)

Whether the seating policy has changed over time is an interesting question. As far as I can remember, the Stake President and his councilors have always sat side-by-side at the head of high council table; and back (eons ago) when I was a child in primary, the Primary presidency always sat at the front of the room -- but other than that, in my Deacon/Teacher/Priest/EQ experience, seating is most often a semi-circle with leaders sitting wherever (though, as expected, they will stand at the forefront when making announcements, teaching, etc...)

Usual disclaimer: I'm not an authority/expert on church policy

I think OP is asking if the EQ Presidency should be sitting "on the stand" in the EQ meeting. Likewise the RS in front of the RS meeting.

I know this was commonplace a generation or two ago...

I think you'll also find that what was "commonplace" likely widely varied from country to country, and here in the USA from region to region (out here in the "mission field" growing up, attending church was quite different than my experiences when visiting extended family in Utah). Years ago, there was a lot of emphasis on what some termed the "unwritten rules" on how the Church should operate. As mentioned, the Handbook currently does not prescribe any formalities for class or quorum meetings (although perhaps there indeed were some kind of official or semi-official guidelines about that in the past).