Is it okay to mix conditioner and lightening powder and developer to lighten hair?

Yes it is okay to add some conditioner to your developer. Everyone knows that lightener/bleach is bad for your hair and dries it out, but there are two kinds of lighteners/bleach, on the scalp and off the scalp. The on the scalp lightener already have some type of conditioning agents in it, not saying that it won't damage your hair but it is better if you use some high quality lightener and developer, as it conditions while it's lifts. You can also add some protein conditioner to your mixture you already have as it will be better for your hair and less damaging.