Hello
Actually I want to get sometime like this:
Horizontal center alignment is pretty easy of setting, however vertical alignment I don't know how I got it


Sorry if it is a stupid question...
Thank you in advance!

I'm sorry that feature is not implemented. Flow hasn't been actively maintained for a while. Calligra project is working on porting to Qt5 right now, I'll see if I have time to do something about it after porting is done.