Hello!
First of all: Happy new year! I wish you all the best for 2019!
I have noticed that the vertical alignment icon disappears whenever I have more than one text element selected.
I still have the possibility to do it via the menu Text > Vertical Alignment but as I need it quite frequently it would be nice to have it as an icon as well.
Btw: In the 1.6 version I have this useful function.
Best regards,
Chris