adding pcie slots
What are the top uses of PCIe x1 Slots?
The most common PCIe slot currently in use are PCIe x16 slots, PCIe x4 slots, and PCIe x1 slots as shown in the picture below.
How do you unlock more building slots? : r/hoi4
Basically, you increase your building slots by adding yourself the spirit (which is doing the job) from the decisions tab.
You will recognize M.2 SSD: why some M.2 SSD have two notches?
If you're simply adding an extra drive to the ThinkPad's M.2 PCIe 3.0 slot, back up your main SSD's important data and proceed with the steps below.