I have been churning away with ideas for cards and I have quite a few that I'd love to send to the development team. Does anyone know how I go about doing this?

Honestly? Win worlds or land a job with them. Not trying to be a jerk but that's pretty much the only way. Their contact rules are pretty clear that they will not accept outside game ideas.

I would probably start with a phone call or email asking if they can take unsolicited game ideas and if they do, do they have the form for you to fill out.

FFG did an entire Cosmic Encounter expansion based on player submissions, so they have done it in the past. They most certainly have procedures to follow, so you probably have to start with someone in legal.

Thank you, both. If only my life/career allowed me to co-design with Jeremy and the team!

Let me know if they do accept unsolicited designs, I have a few cards I've already posted on here that I would send their way

You can also apply to be a playtester. I am sure they are full, but if an opening becomes available, you might get in. Then you are working with Jeremy on a set by set basis.