I had problems with the french version of Dvd architect pro : saving a template was working ... temporaly.
Closing the software, reopening it : my template was no more available.

So, I searched how templates were working.
Making your template always available is simple:

Find the folder containing your template. Make a zip file from these files (the files, not the folder)
Then rename your zip file with a .thm extension.
Put that file in the folder where dvd architect pro stores the temlates.
That is all.
Of course, you cannot erase your template from the GUI, you must erase the thm file manually from it's folder.

Hope this helps.
Oh, where are the folders ?
thm files are stored in program files X86, Sony, Dvd Architect pro 6.0, themes
personal themes are in users, you, application data, Sony, Dvd architect pro 6.0 Themes.
(replace "you" by your account name.)