No editing is done in YT. What's uploaded there is a completed EXPORT of your project.
When Saving in Videopad, a VPJ control file is created. It's not playable, but tells the program how to build the project.
Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. From the HOME tab, the AS choice is available by clicking the caret to the right of the Save Project button on the toolbar. That way you're protected, and shouldn't lose anything. Double-clicking a VPJ file loads the project into Videopad.
EXPORTing creates a playable file, often with an mp4 extension, but many formats and resolutions are available. YouTube accepts these formats. You can export a project directly via the YouTube button or create a video file and use their uploader, as described above.
At this time consider downloading and installing this VP release. Ignore any virus warning. If it does the job for you, stick with it. You can test newer versions, even if unlicensed. For one-time licensed users upgrades are free for up to six months from purchase date. After that, VP will continue to fully function but a fee is required in order to register the newest. Retain your old install file and registration info. If there's an issue, you can always revert.
