I think the handles (hotspots) are auto-created with a 2d point tool (there is a “point” tool inside toolbar palette) before saving your 2d to gsm. Place as many points as you want where you wish your hotspots to appear.
they are the little corners you can turn on under on-screen view options to make it easier to locate the hotspots. this particular symbol is an odd shape so the corners are hard to locate easily. flinging the curser all over the area hoping to find one. i have placed hotspots at the corners when i created the object, but they don't show when the view option is turned on.
MAC Studio 2022 M1 Max, 32 GB RAM, 10 cores, AC26 5003 Apple Silicon USA