The names don’t matter.
Deconz use 2 folders, one of them contain official DDF (that will be replaced at every deconz update), 1 “private” only for your use and this one is probably empty.
Just check if the “devices” folder already exists, don’t create it yourself.
For HA How to add/edit a DDF on Home assistant using text editor? - #2 by Smanar
And do I need to restart deconz or select anything there?
If you are using the GUI, just use “hot reload” in the menu else yep, can restart deconz.