This is subtle feature of using the TAB key that many users are not aware of. First of all, it is easier to see than to describe so you might as well watch the VIDEO.
- Select Entire Chain of Walls or Lines
- Select Partial Chain of Walls or Lines
Second item - Select a wall or line > Hover cursor over a different wall or line somewhere along the path > Press TAB once (Walls or lines highlight) > Left Click to select. The subtle difference is that which direction the selected chain travels depends on which end of the element you hover your cursor over. Watch and then try it!
NO DISCO tabbing, as my friend Cyril says. Just press the TAB key once. You get the disco tabbing when you press and hold the TAB key down. We call it Disco because the highlighted lines will flash at you.
Last comment, make sure you hover and then hold your mouse steady. If you move the mouse away after highlighting the chain the TAB feature fails. You have to make sure everything is highlighted still before using the Left mouse button to select them. It is a process unlike any other software you are familiar with most likely. Practice a couple times if you aren't already very comfortable with it.
Here's the video...