No, it needs to be public to some degree (i.e. "disturb the public peace"):

    § 130 Incitement to hatred (1985, Revised 1992, 2002, 2005, 2015)[38][39]

    (1) Whosoever, in a manner capable of disturbing the public peace:

        incites hatred against a national, racial, religious group or a group defined by their ethnic origins, against segments of the population or individuals because of their belonging to one of the aforementioned groups or segments of the population or calls for violent or arbitrary measures against them; or
        assaults the human dignity of others by insulting, maliciously maligning an aforementioned group, segments of the population or individuals because of their belonging to one of the aforementioned groups or segments of the population, or defaming segments of the population,

    shall be liable to imprisonment from three months to five years.[38][39]

    […]

    (3) Whosoever publicly or in a meeting approves of, denies or downplays an act committed under the rule of National Socialism of the kind indicated in section 6 (1) of the Code of International Criminal Law, in a manner capable of disturbing the public peace shall be liable to imprisonment not exceeding five years or a fine.[38][39]

    (4) Whoever publicly or in a meeting disturbs the public peace in a manner which violates the dignity of the victims by approving of, glorifying or justifying National Socialist tyranny and arbitrary rule incurs a penalty of imprisonment for a term not exceeding three years or a fine.[38][39]

I would not be surprised that it could be considered probable cause to investigate you further. To check if you have links to neo-nazi groups and the like. People don't usually keep those materials just for fun. They usually distribute them.

According to German law - distributing Nazi-related materials in private messages is a crime too.

Germany is a country where this happens: https://www.washingtonpost.com/world/2021/09/09/pimmelgate-g... A dude insulted a politician and the cops raided his house.

IANAL, but the German holocaust rules are about propaganda and I don't think that personal notes that were intended to not be read by anyone else can be considered propaganda.

In Ireland, perhaps soon: Irish Citizens Could Soon Be Jailed for ‘Possessing Material Likely to Incite Violence or Hatred’ - https://www.foxnews.com/media/irish-citizens-jailed-possessi...

If you don't trust Fox enough, their article does link to the text of the bill, directly by the Irish government: https://www.oireachtas.ie/en/bills/bill/2022/105/

I'd link to a more trustworthy source, like the New York Times, but they are curiously silent on this bill.

Here's an example article:

https://www.pbs.org/wgbh/frontline/article/germanys-laws-ant...