I got alot of trimming' from my white widow scrog grow. I was wondering " can the leaves of a plant in veg stage still be used for concentrates... (oil or hash)
Not really, the plant doesn't really begin to produce thc until flowering starts so fan leaves from vegging would have little to no thc. You can try to make hash but you will get minuscule amount.
Last year I saved my trimmings and made cannabis milk tea for Christmas. It was so good and knocked my ass out. I passed it around for my friends to try and it was a huge hit. I'm not a big hash fan, unless it's in keif (powder) form and I can sprinkle it on my bud.