6: Electricity?

My only exposure to electrical theory was 60+ years ago in 10th grade physics. My practical experience did not run to breadboards, jumpers, LEDs (see my previous post), etc. Internet content is great for ease of access but can occasionally be wrong. The breadboard images below make things pretty clear. The left side is less interesting than how the holes are really interconnected underneath.
The bad info I got stated that the vertical outer columns were NOT connected across the gaps that occur every 5 rows. I did some really dumb jumper-ing while I momentarily believed that.

I had not sprung for a DC voltmeter which could easily tested from top to bottom of a column. But then I realized I could make my own:

In around 1956 I bought a cheap soldering iron so I could assemble a Heathkit amplifier. It has been (literally) gathering dust in my workshop since then. The image above shows my crudely soldered voltage tester (cheap LED and matching resistor, pretty useful). This gimmick immediately disproved the false info I mentioned above. The underside breadboard diagram shows that the left and right sides of the board are a) totally separate, b) the outer 2 columns run the length of the board (and could care less which one is positive or negative), and c) the center 5-pin rows are horizontally connected. The red lines I drew on the left breadboard image above are to suggest that it might be cool to connect Pi GPIO pin 1 (3.3V) to the left-most column and GPIO pin 2 (5V) to the "+" column on the right side. I also drew a blue line to the left side minus column (from GPIO pin 6). This I also jumper on over to the "-" side of right edge. Just my way of keeping sane (-ish).

Because of age-related presbyopia I could really use a "large print" version of the breadboard. But that's never going to happen so I keep the magnifying glass close.