CorelDRAW Ideas Portal
My understanding of this, is that if you have two pieces of text in different sized fonts, clicking this button should align them on the same baseline, regardless of whether the text contains upstrokes or downstrokes. In the last few versions I have never been able to achieve this.
If you use the Align and Distribute docker you can accomplish this by 1) Clicking the Baseline Icons, 2) Being sure you're aligning to Objects and then 3) Clicking one of the 3 align buttons as seen in the screenshot.