Yes, keeping a laptop battery at 100% will reduce its life. I’ve seen a couple of laptops come with OEM programs for battery care, in these programs users who will use the laptop mostly when plugged in can choose to only charge to say 70%.
Now I doubt you will see a huge reduction in battery life. My work laptop spends most of its time plugged in at 100%, after 2 years it’s just starting to show signs it’s getting old.