In B4X IDE , and when you are working on multiple projects which have multiple private keystore files, you must switch manually from tools>Private sign key for each project ...
This is a limitation, confusing & time consuming, you should fix it as assign private sign key to the project properties not as universal property for all projects.
This is a built-in solution. It also makes it possible to use conditional compilation symbols to switch keys. It is better than adding more UI options.
B4X:
#If ReleaseWithSpecialKey
#SignKeyFile: ...
#Else
...
#End If