I thought I would add a solution which I've been searching for but eventually figured out. This might be helpful for those of you who have set up a theme in Presenter but then have to install Presenter on a new PC, or maybe have several users who you want to help publish using the same theme. This works with Presenter 9 and probably works on earlier versions too.
Presenter has no import option for themes, only a Save option, so it appears you have to build them from scratch, usually based on an existing default theme. However, it's possible to transfer the theme settings folder from one PC to another. Here's how:
By default a new theme is saved in the User's AppData folder. The file path is: C:\Users\username\AppData\Local\Adobe\Adobe Presenter\Themes (where username is your own name). The AppData folder is normally hidden in a user's folder. In Windows Explorer go to Tools>View>Show Hidden Files, folders and drives so you can see the App Data folder in that file path.
On your existing PC installation find the theme folder you've saved. The folder will be named in the way you've saved the theme. Then, transfer it to the new PC and drop it into the equivalent Themes folder. It will automatically appear in the drop down themes menu on the new PC.
Hope that's helpful folks
Of course if Adobe were to add an Import button in Themes that would be nice ;-)