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Consider the OpenFOAM-v1706 tutorial: /tutorials/mesh/foamyHexMesh/mixerVessel

Therein, the feature lines of shaftRotating.stl were extracted and subsetted via the following group of entries in surfaceFeatureExtractDict:

subsetFeatures
{   
    // Remove the top feature
    insideBox       (-0.1 -0.1 -0.1)(0.1 0.1 0.1);
}   

Say, the user required not to remove (or remove) some other features in the same .stl file. To this end, IMHO, the user likely adds another subsetFeatures entry by intuition. Let add another box into the tutorial's entry, so that it can readily be reproduced:

subsetFeatures
{   
    // Remove all other features apart from the top and bottom features
    insideBox       (-0.1 -0.1 -0.1)(0.1 0.1 0.1);
    insideBox       (-0.1 -0.1 0.8)(0.1 0.1 1);
}   

Yet the execution of surfaceFeatureExtract yields the consideration of only the latter box. The output stream is:

...
Subset edges inside box (-0.1 -0.1 0.8) (0.1 0.1 1)
...

In addition, the simultaneous usage of different entries seems also not possible. For example, when the user enters insideBox and outsideBox entries under the same subsetFeatures, the insideBox seems overriding the outsideBox entry irrespective of the order of entry sequence.

I found a workaround to subset features from several regions on the same surface mesh, yet this requires sequential command executions. For instance, if one wants to remove/add features from two different locations on the same surface mesh, the person can extract the first region through surfaceFeatureExtract with a single subsetFeature. Then, the resulted '.eMesh' files can be used to extract features in the second region through another surfaceFeatureExtract, however, this time using extractionMethod extractFromFile; with another subsetFeature, and so on.

IMHO, from a user perspective, a simultaneous surface feature extraction, which may need to consider multiple region restrictions for some reason, might be facilitative.

Kind regards