Tslop - Nia's finishers were extra. They're good and simple, 10 minute cardio / metabolic 'blasts'. I'm currently using the LWF#2 as finishers - very similar to Nia's, just a little more inventive. Do you have kettlebells? 100 swings with a heavy bell (in 10 sets) is what I turn to when I'm unsure what to try! (I use a 22kg bell - only 5 breaths allowed between sets - it's surprisingly hard.) Or you could jump rope, do burpees etc. It's that sort of stuff that Nia uses. I think its only really necessary if you want to burn fat. The lifting should raise your HR enough for a cardio effect - especially on leg days
Oh, I've just thought - GGS occasionally post ideas for finishers
https://www.girlsgonestrong.com/15-min-bodyweight-hiit-workout/