My personal experience with a Lenovo W520 having the battery needlessly inserted for two years (40 hours per week) while connected to the charger:
The battery lost 50% of its capacity. The laptop was almost exclusively used while connected to the charger.
So if there hasn't been a big change in how laptop batteries work in the last few years I'd recommend removing the battery whenever the charger is connected if possible.
I found that fully discharging and recharging such a battery 3-4 times will bring it back to (near) its original levels.
I've always had laptops plugged in all the time (desktop replacements) for months at end, with the battery acting as a UPS.
When first disconnecting the power adapter, the batteries always discharged much faster than they should. After a few cycles, they went back to normal.
I believe that leaving a laptop plugged in all the time is better for the battery than doing complete discharge-recharge cycles (5-100%).
The battery lost 50% of its capacity. The laptop was almost exclusively used while connected to the charger.
So if there hasn't been a big change in how laptop batteries work in the last few years I'd recommend removing the battery whenever the charger is connected if possible.