Working as Designed.  There might be a third-party add-on that will display the Master POs, maybe Kevin knows.

Master PO's are not real orders until they translate into a Standard PO, so that is why the Master orders don't show up on the Orders tab.  As BigLouie said: working as designed.

The fields you can add to the grid don't have business logic filters applied... Custom Office simply shows you the columns in the table.  It's up to you to know what values are useful.

You might be able to write a script to look for Master PO details, but I don't know of any enhancements that do this for you (...there might be... I've never looked).  If the Master PO's are not frequently updated, you could set up overnight processes to import daily calculated values into a UDF for easy reference.

An Excel query of Master PO data would work just as well too.  Refresh, sort by item, then look at the current values.

a master PO should have the same priority as a subcontract since it is the project managers guide to what is the material list from a given vendor. It should of course be available from the 3-5 orders tab. It's important and should not be excluded but can be flagged as MASTER PO. I spend a lot of time finding master PO's when it could be so simple.

Kenny is right - we need quick link access to the MASTER PO from the 3-5 screen if needed.  Now I have to go to the project work center (PWC) and find the master PO on the Hot list. Then drill down to see the information. And the PWC then prevents some other screens from opening until you close those that have control of the window. Should just give access from the 3-5 screen orders tab.

If you feel you need the information I would contact a Master Developer and have them quote a modification. I would suggest DSD at www.dsdinc.com  

Sage 100 has no "3-5 screen".  That looks like Sage 100 Contractor, which is different software.  You'd be better served by posting your comment in that community.