In the animation tool in studio, disable looping on the animation and export it to ROBLOX again. Then, in a server script when you load the animation on the dummy, you can set the Looped property to true. Here’s an example:
local anim = workspace.Dummy.Humanoid:LoadAnimation(AnimationObjectHere)
anim.Looped = true
anim:Play()
What’s your use case for not wanting loop on the animation object in the Animation Editor but during run time? You could easily enable looping and upload your animation. It doesn’t seem like there’s any difference between looping via script and via the Animation Editor.