You may use a Map for this:

public static String manageFilters(Map<String, Object> lines){
    System.debug('### lines : ' + lines);
    System.debug('### lines.values() : ' + lines.values());

    for(String key : lines.keySet()){
        System.debug('### lines.get(key) : ' + lines.get(key));
        System.debug('### >>> ' + lines.get(key));
        Map<Object, Object> test = (Map<Object, Object>)lines.get(key);
        System.debug('### test ' + test);
        System.debug('### test ' + test.get('ObjectName'));
    }

    return null;
}

Using account id as example is terrible idea because they'll be unique -> your lists would always have size 0. But yes, you should be able to do something like that.

Your stuff doesn't even compile, you can't use "=" in for(Account acc = [SELECT...]).

Let's say you have accounts and some of them have duplicate names. This would be close to what you need:

Map<string,List<Account>> accountMap = new Map<string,List<Account>>();
for(Account acc : [SELECT Name, Description FROM Account LIMIT 100]){
    if(accountMap.containsKey(acc.Name)){
        accountMap.get(acc.Name).add(acc);
    } else {
        accountMap.put(acc.Id, new List<Account>{acc});
    }
}

and then yes, if you'd have the key you can access accountMap.get('Acme Inc.')[0].Id