Architectury 7 is the API version for Minecraft 1.19.3.
Creative Tabs are now deferred on Forge, TabSupplier is introduced in Architectury 7.
Creating a Tab should be similar as Architectury 6, with just the return type changed.
CreativeTabRegistry.TabSupplier TEST_TAB = CreativeTabRegistry.create(new ResourceLocation(TestMod.MOD_ID, "test_tab"), () -> new ItemStack(TestRegistries.TEST_ITEM.get()));
The vanilla Item.Properties.tab() method is removed, you can use Item.Properties.arch$tab() instead, it should accept a CreativeModeTab or a TabSupplier.