First let me say I have been using homeassistant for the past two years but due to the direction they seem to be going and some instability the last release caused i made the decision to move to smart things.
I am looking for some documentation around the features and concepts ( modes, automations and scenes ) and how they relate and are used in smart things.
Secondly there is some functionality i seem to be losing with smart things, but it seems like functionality that should be there so I’m probably looking in the wrong place for it. For example, i found out how to setup an action to be delayed for a period of time. But i need it to be delayed and only fire if the triggering event is still active. For example: i walk into a room and turn on a light ( trigger ) as an action i want my ceiling fan to turn on in 2 minutes but only if the light is still on. Right now, i walk into the room, turn the light on, retrieve whatever i wanted and turn out the light all within 1 minute. A minute later the 2 minute delay runs out and the fan turns on. Where do i ask those types of questions, and is there the ability to extend smart things under the new app?
Thanks
Good questions! The answers are a little complicated, but if you start with the community beginners FAQ, I think it will help:
SmartThings Beginner’s Guide (2019)
In addition, try the community How-To on complex logic rules. I think it will answer your questions about delays and that type of thing. 
How to Get Started Creating Complex Rules in SmartThings (2017) (SmartThings Classic)
As far as where to ask questions, if you are using the official features, ask in the following section of the forum:
https://community.smartthings.com/c/smartapps/automation-ideas
If you are using webcore (essentially a scripting language for smartthings which you will read about in the complex rules how to), they have their own forum. (Again, details in the complex rules how to.)
I’ll leave the concepts to others in the community and I just noticed @JDRoberts answered too. If he answers a question he’s usually right. 
Absolutely, while the automations in the new application are way better than the older Classic app, and worth trying first, it sounds like you’re looking for a conditional rules engine. The SmartThings answer for that is WebCoRE (Web Community’s own Rules Engine) Here’s a link for howto get started:
Note: the instructions are for Classic. You can use both at the same time (just don’t use mobile presence from both apps at the same time, pick one) Once you get it installed for Classic it works under the Custom Automations in the new SmartThings app.
Known issues - there are some things that can only be installed on the new app, if you run into one of those, WebCore won’t be able to access it and use it (New Scenes functionality, new version of the Sonos integration come to mind) We’re all waiting on pins and needles to see how planned updates to ST and WebCoRE announced last month resolve this.
Thanks from another newbie as I was after similar info!
It should probably be clarified that Scenes can be executed from webCoRE, but what you don’t get is an ‘execute Scene’ command in the same way you get an ‘execute Routine’ command, so you have to deal with the detail.