Operator panel?

Sometimes, when I use a tool it’s options who up in the operator panel under the (T)oolbox. Other times they don’t. I just had Bevel showing those in the panel, but now I can’t seem to make it show them in the panel again.

No big, I can still read the tool’s options off the 3D view bar and use the hotkeys to select them, but I’m striving for a deeper understanding of Blender, and that means consistency.

The options are only available in operator panel or F6 when you use the tool. Do any other operations and they won’t be available. Ensure you haven’t hidden the operator panel (+ symbol)

In 2.79 I cannot find the + sign to open the “operator panel”. Pressing T or N does not help. Pressing F6 brings up a popup menu with “delete” in it. I’m following a tutorial that requires the operator panel. Why are the panels not labelled? Even an optional popup label would help.