My Finder window on my iMac insists on always opening in a small window in a corner of the screen. I moved it there one time years ago, and now it is forever stuck there. Sometimes it will stay at the new location/size I move it to for a few hours, but it always goes back to the same old spot at some point.
I have searched and tried every suggestion I can find. The most popular being move/resize it while holding Command, then option-click the dock icon and relaunch. It will work for a day, and then right back. It’s driving me nuts.
When I get a new M1 iMac, I swear I will never move the Finder window again.
The same problem seems to happen across all sorts of operating systems.
I had a similar problem across apps generally. Even when I got them in the position I wanted, in the course of working I’d move them, usually to access another app, and soon my screen (and app default positions) would be a mess again. I solved it using Keyboard Maestro.
Keyboard Maestro has many uses, but this one only occurred to me relatively recently.
It has an action to resize a window, and it’s very simple to create a set of macros to - for example - move an app to the left half of the window, or the bottom right quarter, and so on. (There are downloadable macros in the KM forum that cover pretty much any window position you might want but creating them yourself is relatively easy once you’ve seen a couple of examples.)
Then I created a macro that triggered whenever the Finder activated. It has a single action which was to resize the window to the left half of the screen. I also have similar macros for other apps I use regularly and I want in a particular place (terminal, top left quarter; messaging apps top right quarter and so on).
So now whenever I go to Finder it positions itself in the left half of the screen. If I need to move it - for example to drag and drop a file into another app - then the next time I go back to Finder it repositions itself where I want it.
I suppose everyone has a method. What works for me is to hold Option while I drag the Finder window to the dimensions I want, then close the window. Subsequent windows will hold the same dimensions.
Until they don’t, of course. As @Leeabe51 reports, after awhile the fix stops working. The fix seems to fall out more frequently on Big Sur than it did on Catalina.