Question

How to make the documents from a particular vendor skip the Verification stage?

Answer

In order for a particular vendor to skip the Verification workflow stage, the default entry conditions for it can be changed as follows: the default group of rules "OR" would be placed inside the "AND" group where the Vendors check rule would be used. See the example in the below screenshot.
 

 
For multiple vendors, the "Vendor check" rule should be replaced with the script rule where the vendor name field is checked to be not equal to the selected list of vendors.
 

 

//C# code

string[] vendors_list = new string[] {"vendor_1", "vendor_2", "vendor_1"};

foreach (string vendor in vendors_list)
{
    if (Document.Field("Invoice Layout\\Vendor\\Name").Text != vendor)
    {
        Result.CheckSucceeded = true;
        break;
    }
    else
    {
        Result.CheckSucceeded = false;
    }
}