How do you spawn an sdf in an already running simulation in gazebo garden?

edit

I'll look at that. I also clarified my title

I looked at the UserCommands class and im not sure how to call it? Is there a python api or some other way to call the gazebo service?

If you want to spawn a model from the command line, you can run gz service -s /world/empty/create --reqtype gz.msgs.EntityFactory --reptype gz.msgs.Boolean --timeout 1000 --req 'sdf_filename: "/path/to/model", name: "my_model"'

If you want to do it from C++, here is an example. There is no python API for that currently.

I tried the command you suggested and all I get is "service call timed out"

sudo gz service -s /world/empty/create --reqtype gz.msgs.EntityFactory --reptype gz.msgs.Boolean --timeout 1000 --req 'sdf_filename: "<full_path_to_sdf_file>", name: "diff_sdf_2"'

You need to change the "empty" in /world/empty/create to the correct name of your world. Also, I wouldn't recommend using sudo with Gazebo. Do you get any messages from the terminal that's running Gazebo? It's helpful to run it using -v4.