Where to start with my project

Hello again, sorry for not responding quicker I was given some actual work to get on with last week.

I’ve watched the video you linked above, but again this appears to be how to move something along a specific path, this isn’t quite what I’m looking for unless it’s extending the objects’ size along the path rather than just moving it.

What I’m trying to do is when one of the boxes is selected, lines (or branches) extend from the box outwards to link up with the other boxes to which the selected one connects.
Those lines would remain visible between all points until another option is selected in the menu.

Say for example box 1 is selected and that connects to boxes 3,6,7 & 9. I would want lines that extend from box 1, through the empty space between the boxes and join up with the other 4.