Hey inext,
It's my understanding that mimosas grow in open areas under full Brazilian sun in their natural habitat. I think people assume they're understory plants in the Amazon, hence passing along info that they need indirect light, but knowledgeable people in that region have said otherwise.
Like Hieronymous said, IME they like as much light as you can give them from the time they sprout. I have several directly under a 250 watt HPS light, just inches below the light packed in as close as I can get them. Nothing else I have would withstand it, but they flourish there. They were under a T5 initially, and while they were living, the growth was seriously stunted by too little light output. You always want to acclimate a plant to any change in light, humidity, or whatever, so slowly introduce it an keep a close eye on it during the transition.
You should try to add some wind resistance if they will be indoors. It gives them a little workout to keep them from getting floppy, which can definitely happen.
Good luck! Love growing the mimosas...
Forge a Path with Heart <3