How to secure a door swag so it wont fly around?

I would consider trying command hooks, they make them so they come off easily both hold really well.

You could rig something up with a command hook and a little wire where you can’t see it underneath the greenery

Command strips. Double stick.

https://www.amazon.com/Command-Picture-Decorate-Damage-Free-PH206-14NA/dp/B073XR4X72

Besides the glass, what is the other part of the door made from -wood? metal ?

You can use command hooks

If you want to try something you probably already have on hand use those little bread twist ties. The ones the same color as the swag would help hide them.

Hi Linda, you can weigh the bottom down a little or twist the swag around some wire.

Hello Linda.

Use Blu Tack or something similar or use double sided tape. Seasons Greetings!

an upside down command hook would work at the bottom of the wreath to hold it in place. It should still work on glass. I would at least try it.

I would attach some command strips to the back

Is it inside or outside? I think that might make a difference on what you can use. Some double stick tape should handle the situation.

Clear double sided tape would work. Check out Alien Tape. I really like it and it would be virtually undetectable.

I use a second Command Hook at the bottom of my swags to secure them from blowing around.

I would attach it both top and bottom! You could use a command hook at the top and maybe just a command strip sticky on the bottom with no hook.

Command hooks might work. They are removeable. You could wire the bottom of the swag to the hooks.

You can add a command strips.