I am using ArcGIS Pro to update some of our old poster maps. I am trying to dynamically label individual detail maps on the poster. I have a title for each of the detail maps in a "rectangle text" item. I'd like the text in this item to be vertically centered. Based on the Format Text dialog, this seems to be possible. In fact, it works for regular text, say with a marker background, but not for rectangle text items. Am I missing something?
First, some background since this issue can be quite confusing.
The Text Symbol properties (below) are general properties that can be applied to text symbols that can come up in different contexts such as map labels, annotation and graphic text on a layout. Though most properties, such as the properties under appearance, should work for any context, some do not.
As the you see in the UI screenshot above next to the Text Symbol tab (underlined in blue) is the Text tab. Here we find properties that are specific to the context (or element) that the Text Symbol is being used in. This is key! The Text Symbol (and its properties, in particular the Position properties) don't know anything about the context in which the text is being used.
The Text Symbol doesn't know if it is in a rectangle, or a circle. It doesn't know how much space there is to fit the text. It does know how wide you initially drew the text element and this is why horizontal alignment works. If text flowed vertically we would have the same limitation, but for horizontal alignment instead of vertical. Vertical alignment does not work with paragraph text elements because it was not originally designed to work in this context. And, unfortunately, it is not a simple matter to just get a setting designed for one context to work in others.
I'm sure you have noticed that there are properties for the text element, separate from Text Symbol, that also deal with the position of the text.
These properties are aware of, and specific to the context in which the text is being used. This is way we have 2 different tabs: Text and Text Symbol. One context specific and one more general.
We know that many, like yourself, want the ability to vertically align text within a text element - see Allow Rectangle Textbox to Grow/Shrink and Vertically Justify Text .
As for your request on adding vertical alignment options I would recommend adding your idea to https://community.esri.com/community/arcgis-ideas
Hope this helps,