Whether it's a connection or not is irrelevant. The limit is based on how many segments you have!

Excellent. Thank you.

No, as previously stated you are only allowed 4 flight segments in each continent (6 in North America). The following would work. Routing via KUL from MEL to DEL is also more convenient IMO, but I'm guessing your routing via NRT because you are wanting a mileage run. Add a trip to Alaska in North America if you're going for a mileage run. The following is 13 segments (11 flight segments and 2 open jaws), so you have 3 segments remaining. So if you are looking for a mileage run, then AS flies ANC to/from LAX four days a week; you could do JFK-LAX-ANC, ANC-LAX-SFO instead of JFK-SFO, or SEA instead of LAX as AS flies ANC to/from SEA daily.

OSL-DOH-MEL
MEL-NRT-DEL
DEL-KUL
KUL-SGN

Book separate SGN-CGK

CGK-NRT
HND-JFK
JFK-SFO
SFO-DOH-OSL

Have you checked if there are flights to/from NRT? And not the other Tokyo airport HND. If you end up with a NRT-HND ground segment that counts in the 16, but not in the continent count

Have you downloaded the rules?
FAQ "What are the RTW rules" in OW
https://www.oneworld.com/round-the-world

I'm optimising for destinations I want to visit. Tier points are then secondary, to maximise those within destinations I want to visit, hence why I'm happy to transit via NRT each time. I don't necessarily want to max out the 16 segments if it'll add more days. I want proper visits to Melbourne, Delhi, KL, NYC, SF, Tokyo and Jakarta (i.e. 3 days minimum each) so once you add the travel time, it's really starting to stretch the tri.

I can visit SGN some other time.

Does the burnt sector to switch from NRT to HND for the JFK flight count as a segment rather than a burnt sector out of the 16? If not, why does this not count as 4 Asian segments?

Melbourne: OSL-MEL (transit in Doha)
Delhi: MEL-DEL (transit in Narita)
KL: DEL-KUL (transit in Narita)
Jakarta: KUL-CGK (transit in Narita)
Tokyo: CGK-NRT
New York: HND-JFK
SF: JFK-SFO
Oslo: SFO-OSL (transit in Doha)

I've verified the flights out of NRT. It's the JFK flight that requires a switch to HND.

Read the rules. Ground segments count in the 16 maximum. But not for the continent counts.

Far better if the "transit in Narita" are listed in detail. They count as 2 segments

The rules are complicated and that�s why I�ve asked because there are always nuances. I�ve been told if you are flying KUL-NRT-CGK, that counts as one of the 4 segments. Are you saying that�s 2?

That's 2 flight segments.

KUL-NRT 1st segment
NRT-CGK 2nd segment
Each flight number counts as a segment.
Who was the person that "been told " counts as 1 segment? Ignore what they say.

On some flights like LHR-(SIN)-SYD that counts as 1 segment as would be ticketed LHR-SYD. Just happens to transit at SIN. And some passengers could be ticketed LHR-SIN and get off at SIN.

The rules are not that hard. Just print them out and read them several times. Have to comply with all rules.

Hi obamtl
Here's an itinerary that I think will work for you:It has stops at all the places you want.
It has four flight segments in Asia (SGN-KUL-CGK-HKG and TYO-DEL)
It has the required trans-atlantic flight (SFO-DOH)
It has the required trans-pacific flight (DEL-JFK - which looks like it's not trans-pacific, but is according to OneWorld - I guess because it is from Asia to North America)

Other Notes
Yes the rules are complicated, especially if you are new to them. I recommend the Oneworld Explorer User Guide Wiki, which is more readable.

The itinerary I posted uses only 12 of the allowed 16 segments. Your profile doesn't say where you are located, but if it is in Nth America then you could make use of the four remaining segments to have an extra trip, or two, any time before the 1-year anniversary of your departure from Oslo.

Assuming this trip is pleasure, not business - might DPS be a better choice than CGK?

Edited to add:
I've just realised that Qantas flies CGK-MEL, so HKG could be dropped from the itinerary I posted
Meaning only 11 segments are being used
Which in turn means five segments would be available to use later

Some aspects of the rules are indeed complicated with different airlines sometimes interpreting them different ways.

Most people in this thread will be happy to assist.

This is really helpful, thanks. I’m UK based.

These flights will be credited to BA, hence why trying as much as possible to prioritise JL and QR over other airlines, and why I was trying to use JL to hop around Asia. If a flight with JL from KUL to SGN going through NRT uses up 2 of the 4 Asian segments, then I’ll have to significantly rethink the itinerary as it means hopping around Asia may not be viable using a DONE4.

Now that I have a better understanding of your aims, how about this 14-flight itinerarySalient features:
44,534 mile, 12-flight RTW from OSL to MAN (or any other UK airport to which QR flies)
of which
37,354 miles, 8 flights are on either QR or JL
Plus
6,447 miles, 2 QR flight MAN-DOH-OSL to be taken any time within the ticket's 12-month validity
Plus
According to expertflyer.com QR codeshares on AA's JFK-SFO flights

Off the wall suggestion:
When you are back in the UK, you could change your ticket to a DONE5, and fly MAN-DOH-CPT-DOH-OSL
15,677 miles, 4 QR flights
Incremental cost would be NOK8226 plus taxes and charges