By default ADE will compile everything in the project file except for those objects that are included for information such as nearby airports and stock navaids.  There is an internal mechanism which works out whether something should be compiled or not.  This is called skip compile not really accessible to the user. The conditions in which something gets compiled can change depending on circumstances and in some cases ADE can't determine whether to compile something until it actually comes to compile the project.

It may be useful sometimes to stop ADE from compiling a specific object or group of objects.  You can do this using Force Skip Compile.  When this property is set ADE will not compile the object irrespective of the internal mechanism.   If this is not set then ADE uses the internal skip compile mechanism.  So settings Force Skip Compile to No is not a guarantee that any object will be compiled.  All you can say for sure is if it is set to Yes then ADE will Not compile the object under any circumstances.

This option is not available for all object groups.  It makes no sense to have it for helper shapes, background images and so on because they are not included in the compile.  It is also not available for the taxi and parking network - it would be difficult to predict the effect of not compiling some part of that.  Finally it is not available for custom GP objects and for Terrain Elements.

Please note that you need a ProKey for Force Skip Compile to be available.  If you don't have a ProKey then ADE will automatically set Force Skip Compile for all objects to No.