Hollie --
OK, at my computer. You don't really need Smart Controls. Just use an Automation lane .... its as easy as automating Volume in a track.
1) in Logic, make sure you've selected Show Automation (from the main menu, its at Mix>Show Automation).
2) in the audio channel where you've got your Helix plug-in, use the Automation pull-down menu to select Helix Native, then you should see a list of available automations (Knob 1 - 16, etc .... and Snapshot Index .... etc). Select Snapshot Index.
3) You should then have an automation lane for Snapshot Index, with a line at the bottom for #1. You can click on the line to select other Snapshot numbers, at the time you want them to be in effect.
That's it, really. I'm assuming you're using the latest version of Helix Native. I'm using 1.82 in this example, but I think any 1.8X works just fine.
Hopefully you'll be in Snapshot Automation Bliss soon.
Below are some more screen shots I took when writing this up that might help....