If there is one set of conditions that you'd like to set as your default view in the Purchase Order section, you can 'save' the view for future use.

As an example, to filter out FBA shipments from your Purchase Order overview, click on Filters > Default Warehouse to show a list of warehouses that will be the destination for your shipment. 

From the dropdown, click on your non-Amazon warehouse to filter out Amazon shipments. 

Then click Apply Filters.

To set this as your default view, click on Filters > Save.

Then select your filter name and set as default if desired.

If you would like to set a previously saved filter as a default, click on Filters, hover over name of the filter, click the three dots, then select Apply Preset.