As with , there exists different kinds of tags in minecraft and currently digitality can only add item tags. Here's how:
Item tags
data.itemTag("<tag (without the mod id)>", "<item1 (with the mod id)>", "<item2>"...);
Example
// This code adds the "minecraft:beehives" tag to "minecraft:iron_ingot" and "minecraft:gold_ingot" items
VirtualDataPack data = new VirtualDataPack("minecraft");
data.itemTag("beehives", "minecraft:iron_ingot");
data.itemTag("beehives", "minecraft:gold_ingot");
