I should but mixing climbing/rowing/calisthenics I just don't have enough time to rest and relax.

I mostly try to add some flexibility excersices at the end of my routine, depending on my current goal.

For example, I'm trying to achieve a press to handstand, I know I need more hamstring flexibility for that, so I do some pancake stretching. Like 3 sets of 30s with some weight added. I usually do 2 or 3 of these complementary stuff.