How do you balance life and a second partner?

I am Polyam and married. My wife has a girlfriend and we get along really well.

I want to build a relationship with a person who compliments the parts of me that my wife can't.

I am in a current balance struggle with work being very overwhelming. I find it hard to balance work, hobbies, rest, etc. At least my marriage doesn't suffer due to any imbalance. The integration of our interactions are ingrained in our downtime and it feels effortless.

I'm not hurrying to find someone, but I do feel like I'm consistently missing satisfaction for some needs.

What ways have y'all found to add a new person in your life while struggling to manage other things? If I have to have perfect balance, I don't think I'll necessarily ever be ready, but I want someone to feel like their time and energy is valued.