That is probably due to you using how I setup the radio panel in my v1 panel :)... the v2 is a little better in how it works but yes still needs to setup an event..
The Simulator does not track this or keep data.... Instead you could look to bind it to another switch and thus in SpadNext just define that switch as the setting for it and thus the position of the switch will maintain it after each flight.. Might also be a good request for persistent global variables in spad...
The default aircraft use a different programming language than the CRJ, which is coded in WASM. Making three-way switches work with up/down arrow prompts is not easily done at this time in a WASM project.
Speaking strictly for myself, I much prefer using the mouse wheel for moving switches even in aircraft that support other ways of doing it. It is my preferred method even in P3D and X-Plane, and has been for years. I find it much faster and more intuitive. Having to hover near a switch with the mouse pointer and wait for a directional arrow to appear seems awkward, and can be difficult in turbulence.
The advisory VNAV does need simecmore refinement. It will probably not be in the upcoming update, since that update concentrates on more serious bugs like the glideslope tracking and throttle control, but it is on the list to be looked at.