Not sure what you are referring to. Please provide more detail.
Hi, I have created a group for testing purpose, but now I don’t know how to remove it
can you help me?
There are a couple ways to delete the group but first you need to delete the automation, then either reboot home assistant or go to Developer Tools > Actions > enter action Group: Remove and enter the Object ID of the group.
Edit 241218: Appears there is no way to delete the group from its entity page.
I’ve deleted the automation, reboot, but the group is still present, under entities and under helpers. It says that is without unique id, so I can delete it as usual. any tought?
Just installed this and ran it, works great for my needs. I was pointing it out to someone on Reddit [Turn off all lights except those with label], and they also asked if it was possible to generate the group based on the state of the lights too. It was pretty easy to add the changes to your blueprint (see my Reddit reply) but maybe you could add it to your official version? 
This functionality needs to be in the core code for the built-in Groups. Then HA’s Groups would be useful / valuable