There are several ways to configure SSMS to point to your own working directory as the default. Here’s the easiest to do it without registry hack. You just need to edit the Visual Studio settings file (XML format).
Open Windows Explorer, and go to (you can force type):
%USERPROFILE%\Documents\SQL Server Management Studio\Settings
Find vssettings file with the latest modification date. The file name should follow the convention below.
Make a backup of that file. It’s an XML format and it’s very easy to make a mistake, but less dangerous than messing up your registry.
Open the file with a text editor.
<PropertyValue name="ProjectsLocation">%USERPROFILE%\Documents\My Directory</PropertyValue>
Save the file and make sure you quit SSMS and reload it before it takes affect.
That’s all there is to it. The next time you open a file or a project, SSMS will look into your custom folder first.