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.
macOS 10.13 High Sierra - 32 vs 64 bit screensavers