I’ve been searching for it in the settings, in the internet, no success.
Every time I open an application (text editor, terminal, gimp, firefox), it doesn’t open centered, it opens in the top left corner. Even if I move the window to the center, it doesn’t save where I put the window. So, if I open it again, it opens again in the top left corner.
Budgie settings also doesn’t have something like that.
I’m not completely sure, but GNOME has the same problem.
I just implemented a “Center Windows” option in Budgie Desktop Settings -> Windows in my latest commit. It’ll be in Budgie 10.5 stable (which’ll be released once translations are up-to-date, I’ll have more on that in a forthcoming Solus blog post).