The highlighted button is called the "net" tool. I didn't like the new icons that were introduced a couple of revisions ago and kept the old icons.
Regarding the INVOKE tool/command:
I f you pick a typical logic gate, the image shown in the library will look something like this:
Note, Vdd and Vss are shown and labeled, "P." But, when you place it on a schematic, you will see just this:
The supply pins are not shown by default.
If you want to see the supply pins, you can enter the command, "invoke IC1 p" Note: "P" stands for power "gate" (not case sensitive). If you look up the invoke command, it will refer to gates. We are not used to talking about the supply being a gate.
Alternatively, you can click on the "invoke" icon, click on the IC for which you want to see the gate, click on the gate in the menu, and get the same result:
That process is easy to remember when using logic chips frequently. I don't use them often, so I keep a cheat sheet.
One use is if you have a schematic and only want to use 2 gates of a 4 gate device. You will probably get erc errors for the 2 gates you don't show. The invoke command allows you to put them off to the edge and remove those errors.
Frankly, I don't see that is is a terribly useful asset, but I live with it.
John