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] Can a Flash-based screensaver store user preferences?
Is it possible for Flash screensavers made with iScreensaver Designer to store user settings/preferences, such as the muting or volume of sound or a background color, to name a few examples?