As given in the PLECS Help Viewer under "Connections", for drawing a branch from an existing connection, place the mouse pointer where it is desired that the branch will start. With the right mouse button or with the left mouse button while holding down the [Ctrl] key (or [command] key on Mac OS), create a branch to a new destination by dragging the crosshairs.
I'm also attaching the "PLECS Cheat Sheet" here for other PLECS shortcuts.
A solid black dot marks a connection between two wires. Two electrical wires merely overlapping on one another without a connection will not have this solid black dot, therefore a curved wire, as shown in your circuit, to mark this distinction, isn't necessary.
An example of an interleaved boost converter is given in the PLECS demo model library. Browse to Window > Demo Models, and search for "Single-Phase Battery Charger". Open the PLECS model and then double click on the AC/DC subsystem to view the attached schematic.