Extending a VFX Duration - 0ceal0t/Dalamud-VFXEditor GitHub Wiki
Looping a Fixed Number of Times
So far, I haven't found an easy way to make a VFX loop a certain amount of times, so you'll need to take manual steps to do so. There are several ways to accomplish the same effect, but I found this one to be the easiest to explain.
The basic flow is copying the items in the timeline however many times you want. In this example, the VFX spawns Emitter 0 with a start time of 5 and an end time of 86. If I want the VFX to loop twice, with each loop taking 90 ticks, you would create another item which also spawns Emitter 0, but with a start time of 95 (5 + 90) and an end time of 176 (86 + 90). You would then repeat this process for each emitter in the timeline however many times you want it to loop.
Looping Indefinitely
For an example, see vfx/common/eff/dk10ht_wra0c.avfx
(the warrior beast gauge aura). For this, each of the particles spawned in the timeline need to have an end time of -1 (so the VFX never ends). And the animations graphs need to be set up so that they loop.