Skipping several routines and randomizing within a loop

If this template helps then use it. If not then just delete and start from scratch.

OS (e.g. Win10): Win 10
PsychoPy version (e.g. 1.84.x): 2.10

What are you trying to achieve?:
I am trying to assign participants to either only see the loop_B1_70, loop_B1_80 or loop_B1_90. Once randomly assigned to one of these conditions, I want the loop to be randomized within.
What did you try to make it work?:
Create inner loops for 70, 80, and 90 conditions and then put an outerloop to code skipping two out of the three loops but presenting one of the conditions.
What specifically went wrong when you tried that?:
Very new to coding within PsychoPy3 and cannot figure out how to code presentation of one loop.

I attached an image to show what my flow looks like right now. I cannot figure out when or what code to add in order to randomly assign participants to one of the 70, 80 or 90 conditions. Any help is much appreciated. Thank you!