(I searched for this myself, I'm not affiliated with the mod) ---------->

History fix mod.
1. Added prestige fixes to the Italian states, now the most likely candidate for unification developed by the ai is Sardinia-Piedmont (need to research nationalism). In a few cases ai two Sicily and Tuscany can also be candidates.
2. added Prussian-Italian anti-Austrian alliance resolution, when Prussia/North Germany is a candidate for German unification and Italy exists or has only one candidate for unification, the two can ally if Austria/South Germany occupies the Italian cultural homeland, the worse the relationship with Austria the higher the probability of an alliance. Once allied, the alliance is stable for 15 years.
3. The Franco-Italian alliance resolution was added, and when Italy was unified or there was only one candidate for unification and pan-nationalism was unlocked, Savoy and Nice could be traded for a stable French alliance for 20 years (with Lombardy's claim). Probably agreed when France and Austria are not on good terms. 4.
4. Adding the Italian War of Independence resolution, after Italy (or the only candidate for unification) acquires a claim and aligns itself with France, if neither it nor France is involved in the diplomatic game and there is no armistice, alliance or non-aggression with Austria/South Germany/Germany with Venice or Lombardy, you can click on it and automatically start a diplomatic game targeting Lombardy (priority) and Venice (second). game. This corresponds to the historical Second and Third Italian Wars of Independence. 5.
5. Italy and Germany are each founded with a resolution to acquire the claims of lands they have in reality held in their own cultural native provinces (Germany without Luxembourg and Austria, Italy with Istria and South Tyrol, no Corsica or Malta).
6. The relationship between Prussia and all the small North German customs union states in the opening game is raised from 30 to 50, to avoid random events causing them to withdraw from the customs union. (South German relations remain at 30 for all three countries)
7. Small German states will join the customs union of a major German state if they are fully independent or have pan-nationalism and are weak vassals (i.e. customs union, protectorates or tributary states that are not coloured on the map) and have a neutral or higher relationship. If they are nationalist and belong to the customs union of a German power, they become a puppet state. If there is a pan-nationalist state and it is a puppet state, it will be incorporated into the Great German States. Only if the only candidate for German unification is Austria will a small state be incorporated into Austria. Small Italian states that are pan-nationalist and independent or subordinate to a large Italian state will be incorporated into a large state (priority Italy, North Italy into Sardinia, South Italy into the two Sicilies, the incorporated state must be a candidate for unification if it is not Italy. (Rome, however, did not initiate the merger in the case of a theocracy).
8. German War of Unification and Italian War of Unification resolutions are added, available to Germany/Italy or the only unified candidate with pan-nationalism unlocked, declaring a war of annexation against a small country with relations below (not including) neutrality of 3 lands or less and joining both allies. ai is only used if infamy is less than 25 and the other side has no powerful allies.
9. Austria and the Ottomans can trigger a "nationalist wave" when they or their neighbours research nationalism, increasing the negative effects of radicalism and unrest from discrimination and reducing all types of administrative capacity and conscription rates. This could be mitigated by compromise, and could be resolved by reforming cultural laws to accept the majority of nationalities in the country.
10. Add "low fertility" to France (-16% fertility, +10% immigration appeal) and "high fertility" to Prussia/North Germany/Germany and Russia (+16% fertility, -10% immigration appeal). These corrections will be removed when literacy rates, living standards, subsistence farming ratios and technology meet certain requirements. (There are of course complex reasons for the historical population growth of these countries, as well as large imbalances across regions, but I'll leave the simplification here for others to examine)

This mod only cares about national borders, especially in the hands of the ai. It doesn't care about other issues.
No map changes. Try to fit the original mechanics as closely as possible, without forcing land cuts with code.
In principle, try to use mods that are already available in the workshop.
Subsequent updates planned.