Spectrum Spatial (SSA/LIM)

i.e. only query a subset of the data based on a sql query. Example: Find the Nearest Country in a Country layer but only looking for the nearest African country

There is no option to apply filter with Find Nearest and Point In Polygon stage. You can do it through Query Spatial Stage with MI SQL query. For e.g.

Point In Polygon Query:

SELECT Country, Capital, Obj FROM "/Samples/NamedTables/WorldTable" WHERE Obj CONTAINS MI_POINT(${x}, ${y},'epsg:4326') AND Continent = 'Africa'

Find Nearest Query:

SELECT Country, Capital, MI_Distance(MI_POINT(${x}, ${y},'epsg:4326'), Obj, 'mi','Spherical') AS Distance FROM "/Samples/NamedTables/WorldTable" WHERE MI_Distance(MI_POINT(${x}, ${y},'epsg:4326'), Obj, 'mi','Spherical') <= 1000 AND Continent = 'Africa' ORDER BY Distance

I would suggest something else without using the Query Spatial Stage...

I would use LIM Find Nearest or LIM Point In Polygon using a Named View instead of a Named Table. Selecting a View in the Named table selection from the repository inside the Stage Options of LIM FInd Nearest.

The View could be a View of a database table or a view of a Tab MapInfo file - so a query selecting only the data with some characteristic like Country = "Africa"