how do I make one task run after the other even though they do not have any edges between them?

you can use the 

upstream_tasks

 argument:

from prefect import task, Flow

@task
def task_1():
    pass

@task
def task_2():
    pass

@task
def task_3():
    pass

with Flow("flow_with_dependencies") as flow:
    t1 = task_1()
    t2 = task_2(upstream_tasks=[t1])
    t3 = task_3(upstream_tasks=[t2])

ah nice, thanks:)