Do you mean that you want a code to fill out the green trinities collected in the journal, or do you want a code to allow you to perform the different types of trinities before you normally unlock them?
// Can Unequip all weapons (This disables the codes below until the game is restarted)
201EF344 00000000
// Customize which items cannot be unequipped (only for Sora's weapon slot)
// You can have up to 4 item ids (WW, XX, YY, ZZ)
003E3D58 00000WW
003E3D5C 00000XX
003E3D60 00000YY
003E3D64 00000ZZ
// Here are the relevant item ids for Sora's weapons
Kingdom Key 51
Dream Sword 52
Dream Shield 53
Dream Rod 54
Wooden Sword 55
Jungle Key 56
Three Wishes 57
Fairy Harp 58
Pumpkinhead 59
Crabclaw 5A
Divine Rose 5B
Spellbinder 5C
Olympia 5D
Lionheart 5E
Metal Chocobo 5F
Oathkeeper 60
Oblivion 61
Lady Luck 62
Wishing Star 63
Ultima Weapon 64
Diamond Dust 65
One-Winged Angel 66
Any other id will result in no item being affected
I attempted to find a code to fix it for you, but I was unable to over the last couple days. In my testing, the unmodded iso does give you the journal entry, but only if you haven't defeated the Red Armor before. Once you have defeated it, you cannot gain the entry just by playing on a unmodded iso. If there are any tournaments that you have not yet completed, you can try defeating red armor in one of those and see if it makes a difference, but it sounds like you've probably already completed all of them.
I believe that problem comes from the English Patch. If you load your save on an unmodded ISO and fight the red armor it should fill in your journal. As of right now, I don't know how to fill in the journal through codes.
If you want to be able to warp into the fight from any world, you can also use the cross world warp enable code I created, but note that in can be a little buggy.
Mainly don't use it to warp out of End of the World if you decide to try it out.
EDIT: Note that this only seems to work while the boss fight is available normally, so you cannot fight Xemnas earlier than he would normally be available. If you try, you will just end up warping to the room, but the fight won't start.
An updated infinite hp code that has not been fully tested. This code should automatically determine which character slot Sora is in and set his hp and max hp to 255
If this works well, this should be able to be modified to affect other stats / party members
// Infinite HP Sora
602E26A0 000000FF
00020002 0000006C
0000003C 00000000
602E26A0 000000FF
00020002 0000006C
00000040 00000000
// Infinite HP Sora
patch=1,EE,602E26A0,extended,000000FF
patch=1,EE,00020002,extended,0000006C
patch=1,EE,0000003C,extended,00000000
patch=1,EE,602E26A0,extended,000000FF
patch=1,EE,00020002,extended,0000006C
patch=1,EE,00000040,extended,00000000
EDIT: I fixed the bug in PCSX2 and it was merged into the master branch on 09/21/2019, the pnach version will work on any version of PCSX2 from that date or later.
I did some asm hacking over the past two days and created this code to add on to the room modifier.
It allows you to warp between worlds without messing up the textures of the room you warp to.
// Cross World Warp Enable
20112C40 08044B3A
// Cross World Warp Enable
patch=1,EE,20112C40,extended,08044B3A
Edit: I've messed around with it a bit, and some areas still don't like to be warped out of. End of the World is very problematic with the room modifier in general. It has bizarre and lasting effects on the emulator, so be careful where you are warping to/from.
I don't think they are right, the hp and mp should be based on the character slots, so you can't just have a generic give Sora infinite hp, but instead its give character 1 infinite hp, etc. See the in battle codes.
The game loads entities into the game based on the order they are stored in the cell's ARD file I believe. Those are stored in alphabetical order by filename, so in cell's where entities are loaded that have a filename that comes earlier than Sora's, they will get put into that slot instead and the effect will be applied to them. It is a difficult problem to fix since it is hard to check what slot Sora has been loaded into dynamically.
At the beginning of this month I released a public version of the tool and a tutorial showcasing how to use it. If anyone is interested, it can be downloaded from my Patreon site: https://Patreon.com/some1fromthedark (by everyone, no supporter tier required!).