Code generation is the process by which a data model and one or more templates are passed through a template engine. The model is transformed and the resulting output of this process would be code that can be compiled and used within your application.
When an item changes, either by sync or by Rocks, TDS Classic will call the transformation template to re-generate the appropriate items. At the end of each item generation event, TDS Classic runs a template that generates the “header” and then combines all the generated code files into a single code file.
You can perform the same action by right-clicking on the TDS project and selecting the "Re-generate code for all items". Since all this process generates a single file and process throw all the templates so it will generate the code for all the items not for a single file.
So answer for your question is NO, TDS does not allow Re-Generate Code only for one target Item