EvM5_

Thankfully I left a record of this find on the discord server.

Ah I'll leave it to you then, hopefully they make their way to PKHeX eventually as well to allow for full record/progress editing ^^

Can I edit that? Never used github before (lol).

Hopefully this is a good place to add to this with some findings:

First off, for B2W2, the block for Battle Subway starts at 0x21B00 (instead of 0x21D00), but otherwise it's pretty much the same, so just change that and you're good.

0x21D2C was indeed some "Continue" flag, specifically for Single Trains. When I did a full set of 7 wins it changed to 02. I changed the current/record wins to 14 from the info we already had and changed that to 03, and on my next set I got the subway boss (who pops at match #21).

Immediately after unlocking Super Single Train, I changed its current/record wins to 49, and also changed 0x21D36 to 07, and also got the boss at the end of the next set of 7 I did. 

For a full list:

Current/Latest Wins:

0x21D08 - Single

0x21D0A - Double

0x21D0C - Multi w/NPC

0x21D0E - Multi w/ Friend

0x21D12 - Super Single

0x21D14 - Super Double

0x21D16 - Super Multi w/NPC

0x21D18 - Super Multi w/ Friend

Record Wins:

0x21D1A - Single

0x21D1C - Double

0x21D1E - Multi w/NPC

0x21D20 - Multi w/Friend

0x21D24 - Super Single

0x21D26 - Super Double

0x21D28 - Super Multi w/NPC

0x21D2A - Super Multi w/ Friend

"Continue" Flag - Should be desired amount of sets completed +1:

0x21D2C - Single

0x21D2E - Double

0x21D30 - Multi w/NPC

0x21D32 - Multi w/ Friend

0x21D36 - Super Single

0x21D38 - Super Double

0x21D3A - Super Multi w/NPC

0x21D3C - Super Multi w/ Friend

You can basically see that they just move in increments of two bytes, with just a single gap between the normal and single trains. I suspect that's the Wi-Fi train stats.

I am currently in the process of confirming the two Double Trains and the Multi Trains w/ NPC but there should be no reason for the rest to be any different. 

TL;DR Assuming you have a Super Train unlocked, set it's continue value to 07 and it's current/record wins to 2A and profit. You don't technically even need the record wins but might as well.

Huge thanks to Saternoir for finding the initial data >.<

You would have to have access to Vermillion, One Island (meaning you'd need the first pass), and most certainly you'd have to alter one/multiple event flags to get the pokemon center on one Island to work like that. 

Stuff this vague and obvious aren't too much of a help (and I can't help much more than this), but what I'm trying to get at is that this is very likely to really mess with how your story unfolds later on.

That makes so much sense, thanks!

Update: Found the byte in question. 0x21245. Getting an old save without the "new" prompts and checking the byte on that one, the value is FD. I don't know if that is the precise value for every occasion etc, but it's good enough for me. Anyone that knows why it's that specific value is welcome to explain haha. 

From the way I see it you don't exactly know what PKHex is. You're supposed to extract your save from your game, edit it through PKHex on your PC and import it back in. To do this you'll need CFW/Homebrew on your console. 

The TID and SID on any pokemon can be any numbers you want (in the allowed range). If those numbers, the gender and the name of your trainer match, that pokemon will count as yours (meaning it will let you change nickname, normal XP gains etc). Other than that, the TID/gender/name of the OT of the pokemon show up in the summary page, but unless you specifically want the pokemon to count as yours and not as a traded one, the SID won't be seen anywhere else and is basically irrelevant. If you don't know your SID and want to find it, either check a pokemon through PKHex and go to the OT tab, or just go to the trainer info menu from the lower right.

I don't know much about hex editing so this is unknown territory for me. Anywhere I can read about it or I can get an explanation? Sorry.

I loaded an older save where the "new" icon was still there, took a backup, then got rid of it and tried to compare them in PKHex but it says no differences were found?

Not sure if there was anything else I was supposed to do. I can upload the new/old saves here if that helps?

Wouldn't that alter other event flags too? 

Just now, theSLAYER said:

How about simply importing event flags from a save that has logged on before?

There's quite a bit of saves uploaded to our site.

How would I go about that? I save edit frequently but event flags and constants are something I have little knowledge in, sorry. 

A bit of an update: Set myself up on a WFC server and managed to remove the "new" icon from Game Sync settings. Battle Competition is another thing though, since it seems like I'll need a game sync ID to progress far enough in the process that it counts for the "new" message to disappear. So I'm back at square 1. Need a game sync ID.

I did this just yesterday and came across Pikaedit. (Hope it's okay to link files like this). You'll find it under "DLC", and it definitely works.

PikaeditGen5C.zip

I'm starting a fresh White playthrough and by unlocking the online features the options for "Battle Competition" and Game Sync in the title screen have an annoying "new" sign next to them which won't go away. Thought a game sync ID would shut them up. Any tips?