I've asked Claude about how to create chases (effets). Here is his answer, probably interresting for others as well :
"Chases are a type of effect. Effects are edited in the Effects window (View->Effects). You can create effects that are either preset based or channel based. A chase would be simplest as a channel effect. There are, in fact some built-in templates for various types of chases that you can choose from when adding an effect.
Moving light attributes/parameters/subchannels are all recorded into cues, submasters or effects at a percentage. The easiest way to access attributes to record them into a cue is with the Inspector's Channel tab. You can examine the levels of various attributes/subchannels in the main display by switching between them with the buttons or popup menu beneath the display."