I actually don’t think a flowchart is a better way of understanding this way of representing things, because it’s an entirely different way of thinking about it. I just did it, because your comment made me curious for myself.
A much simpler way to grasp it is relatively straigtht forward algebra.
Are you comfortable with how parenthesis work in regular algebra? e.g.
((7+3)/2)+(6*(3-2+5))
If you’re comfortable with that, then these parenthesis work exactly the same way. You effectively do a temporary calculation for the innermost parenthesis first and then work your way outward.
Except that this is kind of a special algebra (called boolean algebra), which works with true/false (yes/no) only.
With regular algebra you remember that 3+2=5 and 10/5=2. and all of those addition/subtraction/multiplication/division tables. And that’s all you have to know to calculate more complicated expressions with lots of brackets, by working your way from the most inner brackets to the outer one’s .
To do that boolean algebra you have to remember only a few very simple building block calculations:
true AND true = true
true AND false = false
false AND true = false
false AND false = false
true OR true = true
true OR false = true
false or true = true
false or false = false
Each line in the PLE has a true or false answer, when Cubase looks at an individual object to decide if it is to be selected. And then you evaluate all of the true and false combinations with AND or OR going from the innermost brackets working your way out.
So for example when the current event Cubase looks at is a Muted Audio Part, then the 7 lines would evaluate like this
(((False AND
True ) OR
(True AND
False ) OR
True )) AND
True )
or put on a single line:
(((False AND True ) OR ( True AND False ) OR True )) AND True )
and now we work on and remove the innermost brackets first
(((**False AND True** ) OR ( **True AND False** ) OR True )) AND True )
evaluating and removing the now innermost brackets next
(( ...... False ....... OR ( .... .False ........ OR True ) AND True )
keeping going
(( ...... False ....... OR ......................True ... ) AND True )
more parenthesis to go
( ................... True ............................. AND True )
and the last step gets us
True
Yes indeed we have a found a Muted Audio Part (since that’s what we decided to simulate).
While this way of doing things takes a little getting used to, it’s the most common way of telling computers how to select things. So once you get comfortable with that way of thinking, a whole world of scripting software opens up for you. The initial pain can have significant rewards, if you’re intrigued enough. Not every musician is and that’s ok, too.
p.s. I hope I didn’t make a mistake like I did in the first flowchart attempt. But if you find a mistake, it would mean that you totally understood! 
