Is it possible to run (from triggers, as a custom function or script) an application with elevated rights? (Preferably without the UAC popup, since DF runs in elevated mode itself already?)
DisplayFusion doesn't run elevated. There are four processes for DF and only DisplayFusionService(a Windows service) runs elevated. DisplayFusion doesn't seem to use the service for triggers.
You should probably create a scheduled task with admin privelages, then start that task from commandline.