Bit clunky, but I just found a workaround. Gist of it is that while Studio One doesn't let us individually store Bus Channel or FX Channel presets, it does let you store those channels if they're lumped into an audio or instrument track preset.
Say you have a simple vocal chain of one main vox Audio Track, an Audio Track for each of the left and right harmony vox, some separate FX Channels that you Send each audio track to, and a Bus Channel that those Audio Tracks and Sends route to. With the Mix view open, (1) highlight each of those channels, (2) go up to the "Track" options in the ribbon at the top of the screen (for whatever reason you can't do this by just right-clicking), then (3) select "Store Track Preset." This will store the entire chain and preserve the routing.
Doesn't have to be a big chain of multiple channels, either. Can be as small as just a single guitar audio track with a Send to a single FX Channel with some reverb on it. If you store those two together as a single Track Preset, you can now effectively recall that FX Channel wherever you want. Want to use that guitar FX Channel on some other audio track or instrument track? Just load in that guitar Track Preset, delete out the guitar Audio Track, then route whatever other thing to the remaining FX Channel.
Clunkier than it should be, and Presonus needs to just let us make standalone Bus Channel and FX Channel presets, but until they figure that out, this works. Hope that helps.