At the present time, iScreensaver Designer 5.2 provides support for macOS 10.13 High Sierra, but there are some functional limitations.
Please read the 10.13 High Sierra Tech Note
as well as the Release Notes
Due to changes made by Apple, iScreensaver Designer version 5.2 does not currently support macOS 10.14 Mojave.
Please read our forum post
for the latest updates.
[Solved] Including Quicktime intsallation into screensaver Installation?
Is there any way to include the Quicktime installation into the Screensaver on Windows?
If the Programm check that no quicktime is installed, the installation starts automaticaly?