I want to always place the bones on the left and right

If it is a humanoid model, it should basically be symmetrical. Then you want to always be symmetrical when moving bones. To use this feature, do the following:

First, load the humanoid model and place the bones as shown below. At this time, the position does not have to be exactly symmetrical. Leave the name of the bone as shown below.

Then open the Bone Configuration Settings dialog.

Select the bone you want to make symmetrical (either is fine), select the opposite bone from the symmetrical bone as shown below, check the mirror type to X only, and press the add button. This will add symmetrical bones to the list, and you can close them by pressing the OK button. (The opposite bone is set automatically)

Then, when you move a bone in the view, you can see that the bone on the other side automatically moves.

This setting can also be used in animation editing.