I have already reported this as a bug. I was informed it's a limitation of Overwolf, and to suggest it as an idea.
My bug report consisted of:
"I want to change the install path of Overwolf to my 2TB storage drive, but when I attempt to change the path it won't look outside my desktop folder. I'd rather not clutter my system drive with modded minecraft folders.
I can't type into the path box or navigate to the proper drive with the change button."
Plus a screenshot I have attempted to attach 3 times.
The reply I received:
"Thank you very much for contacting us, I will do my best to assist you with Overwolf :)
I am afraid that it is not currently possible to install Overwolf on external drives.
We want to improve and make sure our users know that we care about what they want, yourself included.I will personally make sure to forward this matter to the relevant department here at Overwolf HQ, and hopefully we will be able to provide a solution for your needs in the future.
In addition feel free to add your feedback in our idea portal https://ideas.overwolf.com/ :)"