I can't believe this problem has not been addressed since 10 years ago, and also it get worse with the recent UI revamp of the user interface.
All app having a tray icon agent should follow a well-defined behavior when interacting with the user, depending on mouse gesture:
Right Mouse Button
Expected behavior
Show a contextual menu for selecting options
Current behavior
It opens a popup window, user need to press CTRL+LMB to see the menu
Left Mouse Button (single click)
Expected behavior
Show a popup form if applicable
Current behavior
A form is shown, then it is hidden, then it is shown again flashing
Left Mouse Button (Double click)
Expected behavior
Execute a default action
Current behavior
If both open the dropboox root folder AND flash the main form on and off
Please, it's time to address this issue, comeon dropbox.
Right mouse button should show just the contextual menu
Left mouse button should show the control form, with toggle, but without flashing on/off
Double click should just open the root folder, without showing the form
It's all about very wrong tray icon behavior at this time.