Hello, with respect to the new feature of using tabs, it might be a good idea to add a new entry "Edit in new tab ..." to the Win32 context menu. This should - similar to "Edit with existing Vim ..." - open the selected file in an existing Vim but instead of creating a new buffer should create a new tab for the file.
An alternative to this approach would be to provide a configuration option of how to open multiple files in Vim so that opening several files in a single Vim or "Edit with existing Vim..." creates a separate tab for each opened file. I'm sorry if this is already implemented and I was just to blind to find it ;-) Best regards, Lorenz.