Here are all of the cheats/debug codes for EU3:HTTT. As most know, you enter these in the Console Window accessed by hitting ALT+21.
The syntax is as follows:
code <RequiredParameter> [OptionalParameter]
NOTE: Codes and other parameters should ALWAYS be entered in lower-case, with the important exception of country tags which should ALWAYS be in upper-case. (And the '<' and '[' characters aren't entered, they're just used here to denote the parameter types.)
Be warned that as these codes originally existed for debugging, they're not without errors, and you may experience a CTD (crash-to-desktop) or less minor problems. Many codes can be unloaded by repeating the command, but sometimes reloading the save or exiting the game is necessary.
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Cheat Codes (all verified)
authorityGives maximum imperial authority to HRE Emperor.
cashAdds 5000 ducats to treasury.
colonistGives maximum colonists.
conversion_successMakes all currently-active missionaries terminate successfully.
decision <DecisionName> [TargetCountryTag OR TargetProvinceID#]This executes decisions, optionally directed in a different country or a particular province. You don't have to own the province. These are defined in the common\decisions folder, where you can find all the decision names.
die <TargetCountryTag>Kills ruler of target country.
diplomatGives maximum diplomats.
discover <ProvinceID#>Discover a province.
emperor <TargetCountryTag>Makes target country the HRE emperor.
event <EventID#> [TargetCountryTag OR TargetProvinceID#]This executes events, optionally directed in a different country or a particular province. You don't have to own the province. These are defined in the common\events folder, where you can find all the event id #'s. The next post also has a reference for getting useful event ID's.
focus <ProvinceID#>Changes national focus province.
fow <ProvinceID#>Turns on/off fog of war over a province for 1 day (if you're not paused, you might miss it).
government <TargetCountryTag> <Government_Type>Changes the government of target country. Government types are defined in the common\governments.txt file (and are listed below).
heir <TargetCountryTag>New heir is born for target country (obviously, only meaningful on monarchies).
heir_succeeds <TargetCountryTag>Heir succeeds to throne of target country. Note that the current age of the heir doesn't matter.
infamy [amount]Changes infamy by amount. Note that amount can be positive or negative, but your infamy can't go below 0.
influenceGives maximum papal influence.
invest <Tech_Type> <amount>Invests amount into technology. Note that no matter what tech you specify, it's still diverted by what your tech investment sliders are set to.
kill_advisor <AdvisorID#>Kills target advisor.
kill_heir <TargetCountryTag>Kills heir of target country.
magistrate (or official)Gives maximum magistrates.
merchantGives maximum merchants.
mission <MissionName>This executes missions. These are defined in the common\missions folder, where you can find all the mission names.
missionaryGives maximum missionaries.
morehumans <Requires something>The great mystery of our age. It requires a parameter to work, but it's not clear what it is. Based on certain other clues (and the name) it may be related to adding new human players during multiplayer.
nativeSwitches any resident natives to automatically attack once an army enters an "unoccupied" province.
official (or magistrate)Gives maximum magistrates.
pirateAllows pirates to roam (?)
prestigeIncreases prestige by 17.5%.
revolt <ProvinceID#>Spawns a revolt in the designated province. This works for provinces you don't own as well.
spyGives maximum spies.
stabilityGives maximum stability.
tag <TargetCountryTag>This lets the player switch to another country in-game.
SOME CAVEATS: while this command doesn't cause a CTD, it has some minor bugs. Sometimes you may lose national modifiers if you switch back and forth between country tags. More severely, if you switch to a non-active country, your game will be very short indeed.

There are bugs with loading the graphics interfaces too -- you'll notice that if you switch culture groups that the provincial city window will be black as the different culture's window is unloaded. The discovered map of one country will also "follow" you to the new one as the map graphics aren't updated.
tech <TargetCountryTag>This prints a small summary of a country's tech progress to the Console Window.
tiTurns on/off Terra Incognita; that is, it reveals the whole map. It also lifts fog of war everywhere for 1 day. (This will also reveal the whole map for all countries in the world.)
undiscover <ProvinceID#>Un-discover a province.
view <TargetCountryTag>This prints a small summary of a country's savings/spendings to the Console Window.
view_aiSwitches on a descriptive AI mode where you can get lots of information about AI behaviors from a tooltip over their diplomatic shields. NOTE: you have to exit the game to reset this.
Debug Codes (not verified; some work, some may not)
crashThis is a CTD. Possibly useful for either a quick exit

or viewing unedited log files that are normally cleaned-up on program exit.
fullscreenSwitches windowed mode on/off.
reload
reloadfx
reloadinterface (*)*This appears to be disabled.
reloadmap (*)*This may not be the actual command.
set_global_flag <FlagName>Sets a global flag. (Think: Reformation, etc.)
clr_global_flag <FlagName> Removes a global flag.
has_global_flag <FlagName> Checks whether a global flag is set.
windowThis seems to open interface windows from the console. It uses two other commands -- open and close.
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To get additional effects not covered by the codes above, it's sometimes useful to use the event command to execute particular events. A list of useful events can be found in the next post.
Concluding warning--
Be aware when playing around with these that they are not always bug-proof; at worst you could cause a CTD, but you may also experience milder bugs. The bugs may even be erratic: a code may CTD at one time and work fine if you try it again. Beware especially of giving out-of-bounds values as parameters (e.g., giving a negative number for ProvinceID# will cause a CTD).