How to change default install library on Steam
First create an additional Steam Library Folder: https://www.youtube.com/watch?v=_stztuVaBKk
Changing the default install location means that you change which Steam library folder is selected by default when you go to install a game on Steam.
Doing this obviously means you have multiple Steam library folders.
Step-by-step walk-through:
1. In the upper-left corner click on Steam and then Settings.
2. Click on the Downloads tab.
3. Click on the Steam Library Folders button.
4. Right-click the folder you want to make the default install location and select Make Default Folder.
This video was created in relation to the following Steam Guide: https://steamcommunity.com/sharedfiles/filedetails/?id=1912418281
This video was created in relation to the following /r/Steam Reddit wiki page: https://www.reddit.com/r/Steam/wiki/transferringgames