In terms of planning how to get from X to Y via all connections, I suggest Rome2Rio which'll list the trains and connections, but also give you options for flights, ferries, buses and taxis depending what is appropriate for the route you are travelling.. I can't guarantee the cost accuracy, but it is a good first tool to look at.
Example Dingwall to Inverness https://www.rome2rio.com/s/Dingwall/Inverness
Example Thurso to Fair Isle https://www.rome2rio.com/s/Thurso/Fair-Isle
Clicking on the train option for example will give you schedule information and links to scotrail, while the bus option links to the different schedule websites.
To get more trains to or from a station, click on "Explore" in the top right corner. There you will get additional connections from your "to" and "from" locations. For example for Thurso there are the local Scottish towns, but also ones such as Thurso to Penzance (Cornwall) and even Gdansk!