Welcome to the forum jdch.
Unfortunately there's no much you can do about it on a general/generic level. There is no "centre the page/spread in the window" function, but it would be nice to have one.
One thing you can do is close all documents, go to "Preferences / Display" and change the "Left Scratch Space". This will force Scribus to shift the page/spread over to the right but it's not a great solution as you will have to experiment with different values for different documents.
Personally I just keep my palettes on the right but that's not to everyone's taste, and I probably only do so because there's no "centre page" function in the first place.