As far as I know, DotLiquid (using Version 1.8.0.0) does not support C# Dictionary constructs out of the box. They must be wrapped in a Drop-Object.
So I tried to adapt the Answer of Tim Jones for my use-case. Sadly, this is not working as expected, So I hope someone could show me where I'm going wrong here, for I am out of Ideas.
This is (one of) my wrapped model class containing a Dictionary:
public class LegendAdditive : Drop
{
    public LegendAdditive() 
    {
        AdditiveDict = new Dictionary<string, string>();
    }
    public Dictionary<string, string> AdditiveDict { get; set; }
}
The class itself is embedded in a LegendModel containing some other values:
public class LegendModel: Drop
{
    ...
    public LegendAdditive Additives { get; set; }
    ...
}
As you can see, all the Classes are wrapped to be a Drop, which as I know is a prerequisite for using Dictionaries (Implementing ILiquidizable and so on).
In a converter, this Model is filled like this:
public DotLiquid.Drop GetModel(MyObject plan) 
{
    ...
    var LegendAdditives = new LegendAdditive();
    //dbLegend.Additives is a Dictionary<string, string> itself.
    if (dbLegend.Additives.Any())
        foreach (var additive in dbLegend.Additives.OrderBy(a => a.Key))
            LegendAdditives.AdditiveDict.Add(additive.Key, additive.Value);
   ...
    LegendModel model = new LegendModel
    {
        ...
        Additives = LegendAdditives,
        ...
    };
    return model; 
}
And in a class ConvertToPdf, I have a ConvertTemplate Method like this, parsing the template:
public static string ConvertTemplate(ITemplateFileFactory templateFilePathFactory IDropModelConverter modelConverter, MyObject mplan)
{
    //reading my filepath out of the factory here...
    DotLiquid.Template.NamingConvention = new DotLiquid.NamingConventions.CSharpNamingConvention();
    Template templateObj = Template.Parse(template);  // Parses and compiles the template
    Drop plan = modelConverter.GetModel(mplan);
    Hash hashedValues = Hash.FromAnonymousObject(new { plan });
    string ret = templateObj.Render(hashedValues);
    return ret;
}
And finally in my Templatefile, I try to get the Values of this Dictionary like this:
<div>
    <dl>
        {% for add in plan.Additives.AdditiveDict %}
        <dt>{{add.Key}}</dt>
        <dd>{{add.Value}}</dd>
        {% endfor %}
    </dl>
</div>
Now the file is parsing correctly, but all I get for now is this output when I try to access the Dictionaryvalues in my loop:
Liquid syntax error: Object '[18, Stärke]' is
invalid because it is neither a built-in type
nor implements ILiquidizable
Now it seems that I actually get the correct Values in my Template.Parse Method. I'm just not getting them out of my structure, because...? Any help is appreciated. To be honest, I think I am missing something fundamentally here.