I selected the circle tool, typed in 5s to give it five sides. Now every time I click on the circle tool, it’s a 5-sided polygon. How do I get it back to a circle?
Like all tools it remembers the last input until you restart SU.
So simply select it and type 24 enter to reset it to the default 24 segments.
You can’t get it back to a “true” circle since SketchUp doesn’t “do” circles. All circles are just polygons. You can return to the approximation of a circle by doing another “side” by selecting the circle tool, entering “24s”, “48s”, “96s” etc, then proceeding to place your “circle”.
SketchUp DOES keep the idea of “circularity” as metadata for the set of edges actually placed. With the Entity Information tool open, select a circle and you’ll see it described as a circle with a radius.
However, once you do something that “breaks” the metadata, the “circularity” of the set of edges disappears.