They use a curved plastic that when new is fairly flexible.
Over time with age and UV exposure it gets more brittle.
You can take a heat gun on low setting and moving it along the trim a couple of inches up from it warm it and remove it. Be very careful not to get too close or stay in one spot too long, it can melt the strip.
Here is one place I found to maybe get some trim if you need to replace.
Vinyl Trim/Screw Cover - Factory RV Surplus
Chris in Virginia
2006 Sunseeker 3100SS/LTD
2008 Smart Passion Cabriolet TOAD
1986 Honda Helix (Original owner)