Hi. I was wondering if it is normal for a vein to indent or collapse when you elevate your leg. I've been noticing one spot on the inside of my thigh.

Not really normal. When vein are enlarged and varicose they often engorge with blood that drains when the legs are elevated. This is common but not really normal. I would recommend you get it checked out by a vein specialist.
Normal. Veins return blood back to the heart. When the veins are elevated above the heart as in raising the leg when lying, the veins will collapse as the blood in the veins drains towards the heart. The reverse is true when the legs are below the heart.Other factors such as level of hydration, ambient temperature and hydrostatic pressure all play a role but the simple answer is strictly elevation flow, .