GIMP Version: 3.0.4
Operating System: Linux
OS Version: Debian 12 + Lxde (desktop)
GIMP Experience: New User

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How can set the red circle in the center of white canvas?

Set Crosshair guides. you move the circle layer to the centre. You will find it in View list.

I suspect there is more than just a single layer, white canvas, no transparency, circle in one corner.

However, taking the example as-is.

Add center line guides, I use a script, otherwise one at a time Image -> Guides -> Add (by percentage)
Make a selection around the circle and Edit -> Cut followed by Edit -> Paste As -> Single layer
Crop the new layer to size, Layer -> Crop Layer to content
Use the move tool, that shows a little center mark. Move to the guides center point.
Tidy up, kill the selection. merge layers.....

40 second example: https://i.imgur.com/OVjpSIo.mp4

I will attach the crosshairs Gimp 3 plugin. It is by teapot, see: https://www.gimp-forum.net/Thread-Cross ... f-ScriptFu
Unzip and put the folder containing the python .scm plugin in your Gimp 3 plugins folder.

This is only if you are just trying to place a red circle in the center of an image.

1) Create a new image with a white background.
2) Change FG color to red. FF0000
3) Create a new TRANSPARENT layer.
4) Create your crosshair center guides, Image>Guides> Crosshair Guides v3
make sure snap to guides is activated under the VIEW menu.
5) Make a perfect circular selection on the layer. Make sure the Ellipse Select tool is activated.
Select Fixed aspect ratio in the tool options for the Ellipse select tool. Place your mouse anywhere on the image and drag
6) Snap the selection to the center of the crosshairs.(move the selection), in your MOVE tool options area choose move selection.It is the little red icon next to the word move.
7) Select> To path. Stroke the path with red color. Path>Stroke Path, stroke with line or brush.
Select>none
8) While still having the layer with the circle selected, merge the layer down to the white bg layer.
Layer>Merge Down

That's pretty much it. That will give you a perfect red circle in the center of a white image.

Assuming you have your circle on a transparent layer above the background layer.
If it is a white layer with the circle on it add another white layer and drop it to the bottom

Crop the circle layer to content.
Use the align tool that is already in gimp to centre vertically then horizontally (or horizontally then vertically) That will put it in the centre of your base image. Yes align is still in 3.0.4

Once you get your circle to the centre merge it to the other layer

So many ways to do things in Gimp you have to love it.

Hope any of this helps you imager.