Reaper v5.40 x64 Windows 7x64. Unknown if this is an older behaviour or bug.
PremiseI use this Lemur layout and Reaper OSC config to control the send volume levels and mute state of selected tracks.
Bug
MUTE toggling (states which have no feedback commands in the OSC config!!!) use the OSC command /action/41357 , because there are no OSC send mute commands. They work on selected tracks just fine, though I have to peer at Mixer view to see if they worked or not.
Send level control does not work on selected tracks, unlike the MIDI/OSC actions Adjust track send 1 volume (MIDI CC/OSC only) and so on. They work on all selected tracks. This OSC send level control(see below) only works on one track.
Send level control uses the OSC command /track/send/1/volume for the first send and so on.
Bonus bugsChanging the volume with a midi knob via Adjust track send 1 volume (MIDI CC/OSC only) sends the OSC feedback for the send level to maximum values, or what Lemur interprets as the highest possible value.
Track volume changes via Lemur with the mentioned layout using /track/volume, do not feedback in to the Mackie Control Universal fader position with the standard MCU Csurf plugin.