Resolution:
In Designer 5.6 we have provided a property on enabling which you can avoid exporting all the global variables when building a design time library. Please follow the procedure given below:

1. Set the property in designer.tra file:
property java.property.EnableGvarReduction=true
2. Create project1 with a process and some GVs;
3. Check "Export referenced GVars only" and building a DTL;
4. Create another project2, and add the DTL to this project;

Note: In case you are using global variable groups and have referenced one of the GVs within this group then all the GVs in this group will be exported.