@Kevin you’ll need to add them directly onto a single task. It’s been a little bit, but when I tinkered with Sharepoint links as attachments, I just added them onto the first task in the plan. I don’t remember being able to do it via the Attachments tab directly, which was unfortunate.

@Kevin I had the exact same frustration!  And now that are project are created by Recipe Builder - I have lost that ability at the project level.  But luckily like Casey said, even if you add them at a task level - they are all displayed in the Attachments tab.

Can you put the link in a project Note? Once threaded messages in place, this will be a better experience. We use this to place links to our recorded sessions.