Could I request the mother give up her parental rights to stop the continuous court proceedings?

I obtain full custody of my children almost 5 years ago. Their mother has a 20-year drug addiction. She lost visitation 2 years ago due to a failed drug test. 6 months ago, she had an attorney send a letter to me with a "non-negative" urine drug test where she tested positive for a drug she had a prescription for but not for the prescription drug she abuses. Though she didn't comply with the court order of providing a hair strand drug test, her attorney demanded visitation be allowed because of the 'non-negative' incorrect drug test. Then she took me to court to push for visitation. At the time of the hearing, she was unable to pass a drug test of any kind. The constant court proceedings often cost thousands; I want to be able to support my children not pay for legal proceedings. Could I request she give up her parental rights to stop the continuous court proceedings? If she agreed to give up her parental rights and no longer be obligated for the kids financial needs (she hasn't paid for several years regardless of the court order to do so), could she and I put together a notarized letter to the court to finalize the agreement? I would considered allowing the kids see her if she would give up her parental rights even if she couldn't stay clean for longer periods of time with the expectation she be 'clean' during the visits. I want to avoid litigation every year and bankrupting my family when she knows she doesn't want to get clean.