We will use the directory junction method to move the folders to your desired location.

Your saves and mods are located in your "Baldur's Gate 3" folder inside "C:\Users<yourusername>\AppData\Local\Larian Studios"
There will also be a folder for the Launcher, but you can leave that alone.

Firstly, you'll want to back up the "Baldur's Gate 3" folder to somewhere safe just in case. Remember, all your save files are in there!

Now you will pick out the location you want to move the "Baldur's Gate 3" folder to.
For this example, I moved it into the "My Games" folder in Documents on my E: Drive.
So the new path would be "E:\Users<yourusername>\Documents\My Games\Baldur's Gate 3"

Now, go back to "C:\Users<yourusername>\AppData\Local\Larian Studios" (the original location). There should only be the Launcher folder here now.
While inside this folder, you will run command prompt as administrator (open start menu, type cmd, choose run as administrator).

Now enter the following into command prompt (and remember to replace with your own location path):

mklink /j "Baldur's Gate 3" "E:\Users<yourusername>\Documents\My Games\Baldur's Gate 3"

Then press Enter

You should now see a shortcut linking to your new location inside the Larian Studios folder.
Now you can manage all your saves and mods from the new location!