(1)

Suppose that we have a glyph includes a character O with a rectangle beneath.

We want to center rectangle vertically according to character O to produce character "Theta". Here is my way:

Adjusted the glyph width by adjusting left and right side bearings to be equaled 100 each.

(2)

From Tools Menu, use Action> Contour> Rotate … to rotate the glyph contents using the settings as shown in the figure below: Rotation angle = 90, Clockwise, Rotate around: Center of character.

(3)

As a result of rotation we get the figure nearby.

(4)

Press the keys Ctrl + Shift to reach  to Magic Tool in order to select the external black circle and white inner circle (Select character O).

From Edit menu, use Cut (Or use Ctrl + x)  to send character O to clipboard.

So, we have only the rectangle as shown in  the figure nearby.

(5)

Centerline the rectangle inside the cell using: Tools>Action>Metrics and chose  Center glyph as shown in the figure below:

(6)

As a result of centralization we get figure nearby.

(7)

Paste O character from clipboard using Edit>Paste (Or shortcut Ctrl + v) to get the figure nearby.

(8)

From Tools Menu, use Action> Contour> Rotate … to rotate the glyph contents using the settings as shown in the figure below: Rotation angle = 90, Counterclockwise, Rotate around: Center of character.

(9)

As a result of rotation we get character "Theta" as shown in the figure nearby.