Global ports are, as the name implies, ports that are global to all (non-Mackie) Midi buttons and dials. Mackie Control button and dials have their version of "global ports" configuration on the "Mackie" tab.

Global ports greatly simplify updating port assignments for multiple buttons or dials simultaneously, such as when copying profiles from one computer to another. 

Instead of configuring each button and dial to use "StreamDeck2Daw" as the MIDI out port, you can set "Global port 1" to use "StreamDeck2Daw" and then assign all buttons and dials to "Global port 1". If you need to update the port assignment for all buttons and dials, you can change the connection for global port 1, and it will automatically apply to all buttons and dials.

The plugin has 10 slots for global port connections, which can be configured in any way you prefer. The global port configuration does not specify whether a port is used as input or output; it merely assigns a port name to a global port number.

When selecting a port in other buttons and dials, the global ports are prefixed "GP_portnumber_" followed by the port name for the currently assigned MIDI port.

The global port configuration page offers a choice for how port dropdowns for buttons and dials are populated. If you choose to display only global ports, the dropdowns will still show the currently selected port, even if it is not a global port.

Global port information is not stored in the Stream Deck profile because the configuration does not belong to a specific profile or page. Instead, the information is stored in what is called "global storage".

When you copy profiles from one computer to another, you need to configure the global port settings separately on the target computer. The references to global ports in all buttons and dials stay the same, but you need to assign MIDI ports to the global ports again.