Sorry for that. I can't answer all questions anymore since i partially forgot the details.
Even if it's months late, i can answer your question.
MapView tries to find your Civ4 install so it can use the XML files from the extensions and installed mods to provide the toolbars with available units etc.
The drop down can be useful in 2 cases.
a) MapView fails to find the Civ4 directory for some reason.
2) You want to provide a custom directory on your own. Since MapView only needs the XML part of Civ you could pack the (i believe) assets/xml substructure on an USB stick or something and you could work with it, even when Civ4 is not fully installed on the computer.
In the file pulldown menu, there is "set Civ4 directory." Is this used to designate which version/mod's directory will be used by the mapview program when creating maps?
Is this thread still active? Seems like the last few replies have gone unanswered.
Even if it's months late, i can answer your question.
MapView tries to find your Civ4 install so it can use the XML files from the extensions and installed mods to provide the toolbars with available units etc.
The drop down can be useful in 2 cases.
a) MapView fails to find the Civ4 directory for some reason.
2) You want to provide a custom directory on your own. Since MapView only needs the XML part of Civ you could pack the (i believe) assets/xml substructure on an USB stick or something and you could work with it, even when Civ4 is not fully installed on the computer.