At least, copy Templates from the folder \Template
Also, you should be able to copy over plug-ins from
\PlugIns
Copy params.ini if you touched it.
The bulk of settings are in the %appdata%\PLSQL Developer folder.
The whole folder should be carried over to your corresponding folder on a new PC. If your USERNAME changes you might need to do some tuning later. For example, relocate Recall Statement file accordingly to your new USERNAME.
As I understand, you do not need to transfer the registry entries.
Sadly, things are scattered, and there's no export/import tool for settings.