There are a number of ways to achieve this and the following will alloy you to shoe all, just True or Blanks, which I have called False because for the relationship to work there needs to be a value, but you can change this.
What you need to do is create a calculation in your related table that will return a "True" if the filed has "True" in or "False" if not.
cFilter = Calculation (Text)
IF ( Field = "True" ; "True" ; "False" )
Then in the table you want to view the relationship and filter it from create a global field called gFilterSelect
Now in your relationship graph change the relationship that displays your portal to be between the two Filter fields
gFilterSelect -- = -- cFilter
Now on your layout place your gFilterSelect field somewhere near your portal and change the to be a checkbox set and create a Value List with the values "True" and "False" and assign this to the field.
Now when in Browse mode you can show just the True or just the False, or both by checking the tick box.
I hope this does the trick or at least gets you started.