No way to remove multiple transitions.
You can only start a new project without the transitions.
If you had saved Projects as with numbers on the end of the file name, you could step back to an earlier project.
If you find the auto Saved Projects files, you may find one before you added the transitions.
Where the Auto Saved Files are depends on which version of Power Director you have.
Powerdirector 9 Autosave default location.
AutoSave is located in a hidden folder. Use Control panel > Folder Options to show hidden folders and files.
C:\Users\UserName\AppData\Roaming\CyberLink\PowerDirector\9.0\AutoSave
You can change the '9.0' part to the number of your version.
The above works for V9 to V12
Carl312: Windows 10 64-bit 8 GB RAM,AMD Phenom II X4 965 3.4 GHz,ATI Radeon HD 5770 1GB,240GB SSD,two 1TB HDs.