else if (customerEDI == 'T') {
          so2Invoice.setFieldValue('customform', 172);
          if (customerEntity = '2766' || '273084') so2Invoice.setFieldValue('custbodyintegrationstatus', 7);
          else so2Invoice.setFieldValue('custbodyintegrationstatus', 1);
        }

I am a noob, can someone point out to me how to make this set status to 7 is the entity is either of these 2 internal IDs? this apparently does not work and tags every entity as 7

if (customerEntity = '2766' || '273084')

You only have one equals sign so this is an assignment expression. Also

'2766' || '273084'

does not do what you think it does. Without getting overly in depth your code is doing this:

customerEntity = '2766';
if (customerEntity)

What you probably want is this

if (customerEntity === '2766' || customerEntity === '273084')