Hi,

There is some support for shared files but it is a new feature and maybe some improvements would help

You do need to add your own includes to the Visual Micro "Project Properties>extra flags" (or other property)

This example looks for .h files exist in two different shared folders

-I"C:\Users\me\Documents\SharedSources1" -I"C:\Users\me\Documents\SharedSources2"  

If you need .o files to be produced then you must ensure that you have used "Add existing" to include the .c, .cpp or .s files.

more

If you require a .a archive then, if practical, consider moving your shared code into the \src folder (and sub folders) of a new Arduino library. Then use the library.properties text file to specify "dot_a_linkage=true"