If you are running Qlik Sense September/2017 or later, then you can now enter expressions on the Dimension label. If so, enter the following code:

=$(vDimension) 

The result will be as follows:

This displays the selected dimension in the dimension title dynamically. If you are running an earlier version of Qlik Sense, simply leave the label blank. After this, I would suggest creating a textbox explaining the chart, which will display whatever the value is, in the associated listbox. You can also use the preceding expression in the explanation textbox.