It depends on what MIDI commands the BOSS VE-500 supports. If a simple patch select is all that is required, then that makes it easy to load a song in MobileSheets and the patch select command is sent to the device. The other question is, if you select a patch on the BOSS VE-500, does it send a MIDI message out that can trigger something in MobileSheets? If it does not, then that's going to prevent you from being able to select things on the BOSS VE-500 and having it load something in MobileSheets. You can verify this by bringing up the MIDI listen dialog in MobileSheets (MIDI tab, last icon on the right side) and select things on the BOSS VE-500 to see what it sends.
As far as the connection issues you've been experiencing, are you using the Google MIDI library? Did you try switching which library was used if the Google MIDI library did not work for you? Version 3.6.5 of MobileSheets fixed some issues with connecting over bluetooth to MIDI devices, so I'm not sure if that will help you. In general, if you encounter connection issues over Bluetooth, you'd want to disconnect in MobileSheets, unpair the device, pair the device over bluetooth again, then connect in MobileSheets, and then you should be able to send/receive messages. If you connect over USB, it should be a relatively straightforward process. If you use the Google MIDI library, you should see input/output ports show up. Tap them to connect (it will say "(Connected)" after being connected). Then you should be able to send/receive commands. Using the MIDI listen dialog is always a good approach, so I'm glad you did that. If the Google MIDI library isn't working for some reason, you can also try the default library (which is able to connect to some non-class compliant MIDI devices), or the high-performance USB MIDI library. If none of this works, what kind of cable are you using for the connection? The Samsung S8+ has a USB-C port I would assume, so you really shouldn't run into the same kinds of issues that occurred with older micro-USB ports.
I'll definitely keep trying to help you figure this out, as in theory, it should work.
Mike
As far as the connection issues you've been experiencing, are you using the Google MIDI library? Did you try switching which library was used if the Google MIDI library did not work for you? Version 3.6.5 of MobileSheets fixed some issues with connecting over bluetooth to MIDI devices, so I'm not sure if that will help you. In general, if you encounter connection issues over Bluetooth, you'd want to disconnect in MobileSheets, unpair the device, pair the device over bluetooth again, then connect in MobileSheets, and then you should be able to send/receive messages. If you connect over USB, it should be a relatively straightforward process. If you use the Google MIDI library, you should see input/output ports show up. Tap them to connect (it will say "(Connected)" after being connected). Then you should be able to send/receive commands. Using the MIDI listen dialog is always a good approach, so I'm glad you did that. If the Google MIDI library isn't working for some reason, you can also try the default library (which is able to connect to some non-class compliant MIDI devices), or the high-performance USB MIDI library. If none of this works, what kind of cable are you using for the connection? The Samsung S8+ has a USB-C port I would assume, so you really shouldn't run into the same kinds of issues that occurred with older micro-USB ports.
I'll definitely keep trying to help you figure this out, as in theory, it should work.
Mike