Abandon Finland is a decision available to 
Sweden. Sweden will lose its cores on the 
Russian controlled 
Finland, which makes it impossible to attack Russia without getting Infamy. In return, Sweden will get 10 Prestige, and all of Sweden's pops will lose 1 Militancy. The requirements are for Sweden to have less than 40 Prestige (which Sweden already has at the start of the game) and an average Consciousness of 4. The player must weigh the benefits of gaining a Prestige boost to help them into Great Power status earlier and form 
Scandinavia, or getting the Prestige through other means and retaking resource-rich Finland later, infamy-free.
The AI will always take the decision unless militancy is below 4.
Ingame description
Many decades have passed since the defeat of the Swedish armies in the Finnish War, and the passing of our country's eastern half to captivity under the Russian Eagle. Altough reports from Finland speak of widespread discontent with Russian rule, very few seem to yearn for a reunification with Sweden, instead preferring to seek direct Finnish independence and autonomy. Some say it is time for us to abandon all thoughts of a Swedish return to Finland
The decision is placed in the nationalunifications file instead of the Sweden file in the game files.