Firstly : at what class did you add the IsoNote attribute to the P3D Class Definition?
If you added it only to the Support Class Definition, then the Iso.atr should read: Support.IsoNote, not EngineeringItems.IsoNote

If you defined it somewhere else and you're not sure how to define it for the iso.atr You can go into your Iso Title block setup and add the property (temporarily) to your table setup, that will also add it to the iso.atr. Afterwards you can remove it from the table setup but keep it in the iso.atr.



Secondly, @jabowabo used the KpShopItems filter as an example
If you look at your aggregated lists you'll see what filters are actually used. It is based on the list that the Tables are made (BoM - Weld List - Cut Piece List - ....) So if I look at the groups defined in the list and find the group which would contain my support. I go check there what filter I need to modify.
This is for example an out of the box setup:

To be 100% correct, the support filter is also used to determine the dimensions and annotations that need to be placed around your support. If you do not wish those to change. You can make a second filter called fe "SupportBOM" by adding the following code to your IsoConfig.xml
<Filter Name="SupportBoM" Value="Type='Support' AND (NOT IsoNote='NO BOM')" />
Then all you have to do is change the Support filter in your aggregated list to the correct new filter, the existing filter will still be used by your dimensioning and annotation settings.
