Collect your multimedia files in a folder on your computer. If you want to place the content in a subfolder at the root of the disc, create a subfolder within your specified extras folder:
For example, if you specify c:\media\My_DVD_Project\ as your extras folder in step 4 below, all files and folders within c:\media\My_DVD_Project will be written to the root of the disc.
For example, if you specify c:\media\My_DVD_Project\ as your extras folder in step 4 below, placing the files (and folders) you want to burn in a c:\media\My_DVD_Project\Extras\ subfolder on your computer would cause the Extras folder and its contents to be written to the root of the disc.
From the DVD Architect Pro File menu, choose Properties. The Project Properties dialog is displayed.
Select the Properties tab, and click the Disc Properties button at the top of the tab.
Select the Extras folder box, and then click the Browse button . The Browse for Folder dialog is displayed.
Select the folder where your multimedia files are saved, and then click OK.
DonaldT - to correct one bit of mis-information in your last post above.
While DVDAPro does not allow a direct mixed-mode data/video Blu-ray disc to be created in the way that DVD's are usually constructed, this is the effect of a code-bug in the last development period of DVDAPro several years ago.
Actually a mixed mode disc for Blu-ray is an allowable standard and can be created, and played just fine on hardware, both set-top and computer case drive.
In order to create a workaround with DVDAPro - one needs to author in Blu-ray, create a disc image of the result, and then add an additional file folder for the data container.
Indeed, the help file as written which is unfortunately following the data gaff. My clarification stands for those who want to investigate all of the options.