Obviously running “Automations” from Amazon Alexa is a core part of “home automation” so I am shocked (after speaking to customer support) that the functionality does not exist to trigger Automations in the new SmartThings app by an Amazon Alexa routine/speach. I got around this for the last year or so by having them as Routines in the Classic app, which I can trigger from Alexa routines, but now with Classic app being decommissioned we need the permanent fix. Truly, the only thing I am using these for is to switch the Mode my SmartThings is in - so if there is an easy way to do that by speaking to Alexa, please let me know. Either way, long-term, this is a huge gap for everyone and I fear Samsung is not going to be aware of how big it is until the Classic app is actually decommissioned and then a large user population has their automations unable to work anymore. We should not need to use 3rd party handlers (i.e. Ask Alexa - which appears to be last updated around 2016) since they are not supported by SmartThings and this should definitely be core functionality (especially considering it was in the Classic app). Please let me know if I am missing something or how we escalate this to be built by SmartThings before the Classic app is decommissioned and things explode.
The easy way to do this is with a scene. Just add a scene and have that change the mode.
Then have Alexa discover new scenes, and it will discover your scene as well.
You can then activate the scene by name with Alexa. 
Looked into that briefly, directions online weren’t up to date on selection options. Do you have any up to date that I could use as a workaround? Also, still too technical for the average SmartThings and Alexa user and should be built in (as it was in Classic app)
Ah I didn’t see that second option when creating a Scene last…that should work! (but confused why they separate Automations and Scenes now…). THANKS!
A scene is a moment in time that lists the states of a certain set of devices. Like the ceiling light is off, the table lamp is on, the mode is home.
An automation is a rule that is triggered by some event.
One of the things an automation can do is activate a scene. You can also activate the scene with your voice assistant or from the smartthings app.
So an automation is a “If This, then that“ rule.
A scene can be one of the “that”’s. 
For this particular situation, it is built in exactly the same way as it was in classic, it’s just that it’s in a scene rather than in a routine.
Previously, smartthings actually told Alexa that its routines were scenes. It’s the same control structure as it used to be, it’s just now called a scene in the app.