altium designer net tie
If you hold the Control key while clicking on one of the net connections, all of the portions of the board to which that net is connected will be highlighted, and the rest of the board will be masked.
You can also use the PCB Panel. Go to the top of the panel, select Nets, click on "All Nets". Wait for Altium Designer to sort the nets, then click on the name of the net in the center part of the panel. All of the chosen net will be highlighted, and the rest of the board will be masked. All of the objects in the chosen net will appear in the bottom part of the panel.
If you use Edit>Select>Net (hotkey SN) to select a single connection in a net, all of the connections in that net will be selected.