Mpeg-1/2 video formats have “Group_of_pictures_header” which represents GOP type. That header is presented in the Stream Viewer or the Header panel.
If an I frame has an IDR flag for AVC and HEVC video formats, the GOP is closed. IDR flags are presented in the Stream Viewer panel, just navigate to any I frame in the BarChart and the corresponding header will be shown in the Stream Viewer automatically.
You can save GOP structure information using menu File → Save → Index. The SCV file contains the Key column, which means IDR flag for I frames.