Another method that I use is to save complex parts of the formula as user variables. So in this formula I am trying to figure out the default Ship VIA method on a customer. So my rule is going to be to look up the specific value in the pick list mapping table, and if you can’t find it there use a default value we have in another table .  

Basically if A=Null use B, else use A.   

I found that Scribe and the CRM API does not deal with a NULL value well.  So I have used this model for all my picklist mappings.   So If(IsError (A,B,A))  This will tell us A if the value is valid but if it returns a NULL then B will be used.

So here is how it looks:   Complex Version:

If(Iserror(
        DBLOOKUP2( S76,
                 "OrderShippingMethodCode.ShipViaID" , "I", "InfuseMappingCRMtoSolomon", "FromValue", "Entity", "ToValue" )),      

Dblookup2("Solomon",
                   "ShipViaID","I","InfuseSettings","System","FieldName","FieldValue",
        DBLOOKUP2( S76,
                    "OrderShippingMethodCode.ShipViaID" , "I", "InfuseMappingCRMtoSolomon", "FromValue",  "Entity", "ToValue" ))

Simple Version:

If(Iserror(CRM2SolShipViaID), DefaultShipViaID, CRM2SolShipViaID)

Each DBlookup is made into a Variable, and then this becomes a much simpler formula to work with, and modify.