Have an alternate skill icon to indicate a tag (conversion) change for skills that change from their default damage into void or fire or other tags.
Here’s a mockup as an example. Lunge converted to Void damage and Hammer Throw gaining the void tag with Disintegrating Aura node.
https://i.imgur.com/VxniT3M.png
It’d be really pleasing aesthetically. You don’t need to put that much effort into it, just changing the hue of the already existing icon is enough.