In order to move a terminal around the edges of a subsystem, place the mouse over the terminal and then hold down the Shift key while dragging the terminal with the left mouse button. This approach is used for any subsystem terminal independent of terminal type (e.g signal, electric, thermal).
The video below shows that when the cursor is first placed on the terminal it turns into a cross symbol indicating that a click and drag will connect the terminal to another component. After pressing the Shift key and holding down the mouse button over the port, the cursor icon changes to a circle indicating the new position of the port.
Note: In the bottom left-hand corner of the PLECS window a tool tip appears when the mouse hovers over the terminal, reminding users of the different actions they can take.
If the cursor icon doesn’t change when the Shift key is pressed, then the Subsystem is protected. If you define a mask icon for a Subsystem block, PLECS automatically protects the block and the underlying schematic. You can no longer resize the Subsystem block or move the terminals. The purpose of this protection is to prevent the user from making unintentional changes that might render the icon useless.
If you want to change a masked Subsystem block, you can unprotect it by right-clicking the block and selecting Subsystem + Unprotect or by selecting the block and navigating to the Subsystem section of the Edit drop-down menu. You can later protect it again by choosing Protect from the same menus.