Northeast Scotland has a fairly continuous coastal path with 10 stations along it.  Five of those sections are short enough to walk in a day.

Southeast Scotland is one of the best UK regions to walk by rail, with 24 stations well-spaced along it.

West Scotland has a long coastline with many sea lochs and inlets, and much of the southwest is walkable by rail.  There are 23 stations along it.

This webpage, from Scotland's main rail operator includes descriptive information on several walks from and between railway stations (but with no maps or gpx files).

Ten linear and circular walks you can reach from Scotrail stations, across the country with gpx files, although they really want you to download their app!

Walks from and between Gleneagles, Dunblane and Bridge of Allan stations, on the line from Edinburgh Waverley.