Turn on the "Snap Centres of Objects" button to make the centres of objects snap to a node. There are other snap settings too that are off by default, and their names are visible when you hover your cursor over them.
Also, when drawing the circle you can hold Shift to make it draw from the centre, rather than from the corner of the bounding box. Combine it with Ctrl to make it easier to draw a perfect circle.
Beginners' Questions Positioning circle by its center
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How can a circle be positioned by its center?
I want to draw a circle around a node of a path.
Turn on the "Snap Centres of Objects" button to make the centres of objects snap to a node. There are other snap settings too that are off by default, and their names are visible when you hover your cursor over them.
@tukykarmakar Many thanks mate
Also, when drawing the circle you can hold Shift to make it draw from the centre, rather than from the corner of the bounding box. Combine it with Ctrl to make it easier to draw a perfect circle.
Thank you Xav, this also helps a lot.