How to disable charging on MACBOOK pro with charging cable still connected?

This is how the OSX controls the battery charging when the MBP is connected to the charger.

The battery will reach the 100% level and then the charging of the battery will stop but power will be supplied to the MBP.

The battery will slowly discharge as if it were stored on a shelf.

When the battery charge level drops to about 95%, the battery will start to be charged again until it reaches the 100% level.

As long as the charger is connected, this cycle will continue.

The only control you have is the ability to connect or disconnect the charger to the MBP.

If you choose to keep the charger connected all the time, at least monthly run on battery alone to about the 40% charge level. This will help to maximize the battery life. Avoid deep discharges, they shorten battery life.

Ciao.

There is circuitry builtin to prevent battery from overcharging.

Once charge level reaches 100%, battery will stop charging,

All about batteries:

https://support.apple.com/en-us/HT204054

I charged the battery to full -100%.

The graphics looks like this.

But wait, graphics may differ from model to model.

Try a SMC reset.

Reset SMC. Choose the method for “On Mac notebooks with non-removable battery”.

https://support.apple.com/en-us/HT201295

After a while I will recharge the battery and take a screenshot and post it here.

Fully charged

Running on battery

Charging in progress

Try resetting SMC.

If this doesn't help contact Apple.