As new DLC updates came out, revisiting locations became necessary. Keeping track of new items and locations available in each region, what's finished and what's still missing: this is a big challenge for me. That's why I've put together the simple list below for an organized overview of tasks and items that can be managed through the "General Notes" interface. The list includes important and rare items from the base game and DLC parts 1–6 (Forsaken Airfield, Signal Void, Frontier Comfort, Buried Echoes, Last Horizon, Broken Silence), as well as story-related items and locations based on the information available from the following links (many thanks to the creators):

https://thelongdark.fandom.com/wiki/Tales_from_the_Far_Territory
https://www.youtube.com/@Bashrobe/videos

https://www.youtube.com/watch?v=v_H3dLlQMW0
https://www.youtube.com/watch?v=hXm_9-pw22E
https://www.youtube.com/watch?v=MT7tQx8doq8
https://www.youtube.com/watch?v=qd_NYAUMliA
Updated bunker locations (Prepper Caches):
https://www.youtube.com/playlist?list=PLcbQYTyuKQ1WXAMZP8ToLTPpqak0hc3vm

Information about memento locations can be found at the following link: https://thelongdark.fandom.com/wiki/Mementos

Guide for DLC tales story walkthrough:
https://thelongdark.fandom.com/wiki/Tales

Another post of mine where you can find detailed maps for TFTFT regions:
http://steamproxy.net/sharedfiles/filedetails/?id=2899955301
17/07/2023 List and links updated.
23/01/2024 List updated with Zone of Contamination region.
05/02/2024 List and links updated with unique cooking recipe and insulated flask information.
12/09/2024 List updated with Sundered Pass region and some minor changes.
15/12/2024 The list has been changed with some items from the Broken Silence update.

Abbreviations used:
recipe = Unique Cooking Recipes (9 can be found + 4 from trader)
sw = Short Wave (introduced in the Signal Void storyline)
bunker = Prepper Caches (6 empty + 3 from Hunter, Survival, Kitchen, Conspiracy variants)

*** SPOILER ALERT ****

SP
sw cache – – –
crashed plane –
old house key –
foreman's technical log – – – –
foreman's polaroid – – – – –
rüdiger's diary – – – 
rüdiger's watch –
security chief's id badge –
tactical gloves –
tactical jacket –
camera –
polaroid – –

ZOC
sw cache – –
crashed copter –
foreman’s key –
mine office key –
mine gate key –
lockbox key –
page from a journal –
foreman’s site reports – – – –
security chief’s logs – – – –
security chief’s remains –
faded photograph –
my testament –
respirator –
bolt cutters –
foreman’s tool belt –
insulated flask (green) –
trader radio –
chemical boots –
miner’s flashlight –
woodworking tools –
sport bow –
polaroid – –

FA
recipe (camber flight porridge) –
sw radio +
sw transmitter (covers the Far Territory) +
sw bunker omega –
sw cache – – – –
field 31 operation memo –
security chief's log – – – –
interview transcript – – – –
rifle holster –
sport bow –
insulated flask (red plaid) –
trader radio –
polaroid – –

TP
trader radio –

FRBL
miner’s flashlight –

MT
recipe (lily's pancakes) –
sw transmitter (covers HRV) –
sw cache – –
paradise meadows farm key –
bunker –
insulated flask (jackrabbit) –
trader radio –
polaroid –
memento cache – –
memento hints –

HRV
recipe (stalker's pie) –
sw bunker gamma –
sw cache – – –
bunker –
crashed plane –
woodwright's bow –
moose hide satchel –
polaroid –
memento cache – –
memento hints –

FM
sw transmitter (covers BI and BR) –
sw cache – – –
bunker –
crashed copter –
polaroid – –
memento cache – –
memento hints –

BI
recipe (dockworker's pie) –
sw bunker alpha –
sw cache – –
bunker –
cannery door (aurora) –
forester's revolver –
insulated flask (green) –
trader radio –
polaroid –
woodworking tools –
memento cache – –
memento hints –

BR
recipe (breyerhouse pie) –
sw cache –
trader radio –
memento cache – –
memento hints –

PV
recipe (thomson family stew) –
sw transmitter (covers ML) –
sw bunker beta –
sw cache – – –
bunker –
prepper's abandoned cache –
spelunker's lantern –
insulated flask (orange) –
trader radio –
polaroid –
memento cache – –
memento hints –

ML
sw cache – – –
bunker –
crashed plane –
trader radio –
polaroid – –
memento cache – –
memento hints –

Carter Hidro Dam & WR
Vaughn's Rifle –

DP
recipe (coastal fishcakes) –
sw transmitter (covers CH) –
sw cache –
insulated flask (purple) –
memento cache –
memento hints – –

CH
sw cache – – –
abandoned mine elevator (aurora) –
barb's rifle –
crashed plane –
trader radio –
trade drop box –
polaroid –
memento cache – –

BRM
sw transmitter (covers AC and TWM) –
sw cache – –
bunker –
prison workshop door (aurora) –
elevator crank –
ballistic vest –
warden's revolver –
insulated flask (red plaid) –
trader radio –
polaroid – –
memento cache – –
memento hints –

AC
recipe (ranger stew) –
sw cache – –
bunker –
crampons –
technical backpack –
curator's rifle –
woodworking tools –
polaroid – –
memento cache –
memento hints – –

TWM
sw cache – –
bunker –
expedition parka –
crampons –
insulated flask (white) –
spelunker's lantern –
polaroid – –
memento hints – –

Other rare items:
flight jacket – (various locations)
aviator cap – (various locations)
technical balaclava – (sw caches and inside Bunker Omega)
hunter's revolver – (can be found in bunkers)
prepper's pie recipe – (can be found in bunkers)
insulated flask custom sticker variant – (from trader)
hidden cache (at least 1–7 spawns in AC, BRM, BI, HRV, SP regions, depending on difficulty)