Checking the GridColumnType using a switch statement
The only possible solution I can come up with, to shorten/simplify your code, is to extract the redundant code and place it in a separate method TryAddFilter for example:

private void TryAddFilter(FilteringNode node)
{
    if (filterColumnType != typeof(node))
        filters.Add(columnFilter);
}


And then call this method from the switch-statement:

switch (gridColumnDataType)
{
    case "System.String": TryAddFilter(RuleTextNode); break;
    case "System.DateTime": TryAddFilter(RuleDateNode); break;
    case "System.Boolean": TryAddFilter(RuleBoolNode); break;
    default:
        if (gridColumnType.IsNumericType())
            TryAddFilter(RuleNumberNode); break;
}