How can I command my Lenovo laptop — NOT a ThinkPad — to stop charging the battery, at a maximum cap level of my choice?
Update, after Olin Lathrop's answer.
I phoned Lenovo Technical Support to ask why the "Battery Charge Threshold" in Olin Lathrop's answer doesn't appear in my Lenovo Vantage. Their engineer accessed my laptop remotely, confirmed that "Battery Charge Threshold" (henceforward BCT) doesn't befit my model because BCT is available merely for ThinkPads. Then I asked — why on earth can't BCT be universalized to all Lenovo laptops???
She escalated to her supervisor who didn't know the reason. He concluded that he will escalate my request to Lenovo's engineers, but he can't promise any changes that shall take at least 6 months.
What — (preferably) free — programs can I use instead? What 3rd party programs automatically stop my laptop's battery from charging, at a percentage that I pick?
Battery Limiter doesn't answer my question, because it requires you to "manually unplug or plug the power cord into the laptop."
To make this feature user-friendly, a device should feature a “Long Life” mode that keeps the battery at 4.05V/cell and offers a SoC of about 80 percent.