When I switch libraries using the SBC (Duet 7.4.2), the My Music listings do not dynamically update to reflect what is available on the current SBS. For example, I use the Mult-Library plugin extensively and it should drop those library selections which are not available on the SBS that the SBC switched, too. 

Instead, if the sub-libraries are the same names on both SBS', you have to navigate to the sub-library to confirm whether it works on the selected SBS. This creates a source of confusion as you cannot recognize which SBS your connected to by quickly looking at the My Music selections(i.e. Mult-Library selections.)

This may be a problem with Multi-Library plugin but I'm not sure. 

For example:

SBS I with Multi-Library selections:  A, B, C

SBS II with A, B, E, F.

The controller, no matter which SBS you are connected to, will display under My Music the sub-libraries for: A, B, C, E, F -- which is confusing. In my case, I have sub-libraries for kid's libraries and add'l sub-libraries on music that they share. When they switch between SBS's the display of the orphaned sub-libraries can become confusing.