Center text inside a button

Thanks for your help, yes i guess it depends on the font..

You can change the size of the text box without changing the font size by either creating area text (draw out the rectangle with the text tool and enter the text there) or select your existing text and in the Text section on the right, click on Fixed Size (icon is a box with lines inside representing text). Then you can center it based on the new size of the text box.

Your text object is centered correctly, but your font has an uneven top and bottom margin (blue outline around text). There is no easy way to center text itself unless Adobe makes XD to consider letter height instead of text object's height.