Most of the double terminated “straight” pendants have an option to buy those with an adjustable cord. The cords are a permanent part of the necklace. You cannot swap the cord with other necklaces. If you want to swap, then buy the pendant without the cord (if this option exists) and buy a clap cord or silver chain.
This post shows you the different looks courtesy of my model, my niece Hunter.
Here is the video on how to “open” and “close” the length of the necklace cord. Sorry but the iPhone inexplicably makes this in HDR format and flips 90% : https://youtube.com/shorts/sTA6S_U5eoc