yes u can add it mid game
in theory u should be able to remove it too, modifiers should just disappear but .... it's eu4 so who knows XD

can i add this midgame or do i need to start an entirely new game for it to work?

Some modifiers doesn't add previous modifiers bonuses.
For example; While Institution Spread Fund 4 gives 80% Institution Spread increase, Institution Spread Fund 5 only gives 10%. An 70% decrease.

@Issandii
Great mod and good compression of modifiers.
Adding those modifiers would be awesome:
-Diplomatic Relations
-Missionary strength

Also, I think a missionary strength modifier would be very useful. There are not many ways to get bonus missionary strength and with how much the ai loves to dev its provinces now it would be very much appreciated.

A way to pay for army tradition as well would be very helpful. Either a modifier adding or reducing decay or even buying it outright would be a vast improvement.

So I have some feedback. The development cost modifier is insanely OP, 100 ducats for 20% reduction is way too much. I don't know how far it goes but intervals of 1k ducats for 5% reduction is more reasonable.

The flat boost to governing capacity is also too much in my opinion. The way the original mod did, adding a modifier of around 10% to your existing capacity is more reasonable. Getting over 1k flat capacity which can be boosted even further with admin ideas is way too much. Especially considering you can barely get that from empire rank, mid game tech bonuses, and full estate privileges combined.

np :))

Strange. The old file definitely had commas in the dev numbers. But now everything works correctly. Thanks.

Nope I used dot not a comma ( . not a , ) but I think it's modifier was local dev cost instead of dev cost
I hope it's working now ;P (coz for me it is)

Development cost probably not working correctly because you used a , instead of a . in the numbers. E.g. -0.8
If you want to change it yourself, you can find the data in Steam\steamapps\workshop\content\236850\2607515353\common\event_modifiers.

The development cost doesn't work

dev cost doesn't seem to actually work :/

What are u even doing for your vassals in first place to need -500%?
And what are u talking about "not a new modifier" ? :)

Not a new modifier or a bug, but right now the limit for subject LD reduction is -150% and it would be cool to go at least to -500%. Or maybe LD by development reduction (has a big effect).

Looting Speed increases Available Loot, but other than that it works well