It has always been recommended when new versions of the compiler are released that previous versions are retained in case of compatibility issues.  

Positron Studio allows the user to keep a list of paths to previous versions of the compiler which can be accessed from the Compiler Path drop down on the Tools Dialog/General Tab.  This enables quick switching between compiler versions. 

Two buttons alongside the Compiler Path Drop Down allow users to manage this list of saved compiler paths.

You can Add a new compiler path using the Add button.  
Conversely use the Remove button to remove the selected compiler from the list. 

Note - You can only remove compiler paths which have been added using the Add button.