"When an item is created or modified" is a trigger that will start a flow.
I don't know what is supposed to happen when a SharePoint trigger is put inside during a flow. I'm assuming it stops? Delete the trigger inside the flow "when an item is created or modified".
Either way, you don't put a trigger inside of a flow. If you create an item in step "Create Item" then you just use the outputs of "Create Item A" in the rest of your flow. The values should be the same as if you "Get Item" or even if it was to trigger the when an item is modified.
So you can Create Item and then use the values from the "Create Item" as the values for the condition.