I like what this add-on can do but it is EXTREMELY laggy and unresponsive. I even turned off tab previews and tab details which helped a bit but it's still extremely laggy. I'm running on a MacBook Pro 2019 model with an 8 core CPU, and when I open this extension's popup window, it nearly pegs an entire core. I'm usually around 5-6% average usage on my CPU cores during normal browsing, but when I open the popup it shoots up to 15-25% average. You do the math. To be fair, I have 8 windows open across 2 Spaces, but each window has less than 12 tabs, and honestly if you're using a manager extension like this you've probably got at least half as many windows and tabs as me. I hope the developer works on improving the performance of this extension. It's very nice and only hindered by the performance. I will still use it.

edit: thank you developer for the response. I look forward to any and all performance improvements!