Stephen, don't try to place the Brave launcher directly where you want it. Instead, you can place that App launcher anywhere that is allowed on the Panel, then move it to your desired placement position.
Have you tried that?
Just make sure the icons where you want to move it are all "unlocked".
Just be sure to save the new layout afterwards. 
Maybe you need to check out this earlier posting:
I didn't see anything too explicit, but maybe a review of that code would help.
There is also this helpful "Intro" previously posted by Eugene: