On Dynamics 365 Business Central when use advanced filter and add Vendor No it work as expected, however if you try to use vertical bar | and add lookup via drop down selection again the first filtering is replaced by the lates selected vendor. 

It will be very useful for the partners and customers when use drop down selection and add special characters like vertical bar not to replace but rather to add to the previous value. ( For example if you add A| and then from the drop down if you choose B the result to be = A|B )