Hey Stuart, hey all,
this is not possible with cheap chinese VFDs (except in manual operator mode, but not with the VFD in ModBus mode), but it is possible with Omron MX2 (PDF Manual) or a Hitachi WJ200 (PDF Manual) (which are practically nearly identical). With these, you can override the ModBus control by CNC controller at any time by a switch wired to the VFD and pause the spindle after having paused your g-code program in the Onefinity Controller, e.g. over night, and switch your spindle back on prior to resuming your program next day. This is described here and here. Note that this does not work with cheap chinese VFDs! With these, you would have to run the spindle all night long / during the entire pause as you cannot override ModBus with them, nor can you switch the VFD off during pause, because when switching it back on, it would have no run / speed set prior to you resuming your g-code program (however unlike the hand trim router, a spindle is so silent that it would not be a problem with noise if it runs all night long with no mechanical load – just in case you want to use cheap chinese stuff)