Possible to integrate this with the addon Cell? It works fine in ElvUI for example but on the Cell frames nothing show up.

ClassicHealPrediction adds healing predication only to the Blizzard frames. ElvUI has its own healing predication implementation, you don't need ClassicHealPrediction for that. Cell would have to implement healing prediction themselves as well.

This is not correct. Your addon adds HoTs to the ElvUI frames as well, their healing prediction does not include HoTs but when downloading/enabling yours it shows up on theirs aswell. I am 100% sure of this.

I did not not this was the case. I suppose ElvUI reskins the Blizzard frames somehow instead of creating their own frames like Cell, which I expected ElvUI to do as well. The interaction of ClassicHealPredicition with ElvUI is entirely unintentional.

Okay, thanks for reply.