I've been using bandwidth meters since the 90s, but never got around to making my own. Never needed to until Bitmeter was abandoned. I have a bug report and a suggestion for you.
Bug: Disabling 'Always on Top' prevents NetWorx from displaying the graph over open windows when clicking the tray icon. It opens and closes normally with 'Always on Top'. It will open when you right click on the icon, but then you have to close the menu. I don't want the window always open, but I also don't like having to go back to the tray icon to close it every time ('Always on Top'). When functioning correctly, opening it once should be all that's required.
Feature request: An improved animated tray icon that's more attractive than an empty black box. The long defunct Bitmeter could be used as inspiration here. It's icon was attractive and perfectly functional. I would love to see something similar in NetWorx.
Thank you for the feedback. Regarding the bug when 'Always on top' is disabled, it seems to be some kind of a side effect, in that right-clicking the icon also brings up the graph (something that Windows does behind the scenes). A right-click is only supposed to open the menu and nothing else. The best way around probably would be to have "Always on top" enabled, and assign "Usage graph" to a single or double-click on the notification area icon. Then whenever you want to see the graph a single/double click will bring it up. Another single/double click will hide it. Alternatively you can choose a hotkey.
Regarding the animated tray icon, I'm not sure what empty black box you are referring to. There are three different animated icons in NetWorx that can be selected under Settings - Graph - Graph in tray icon. Alternatively, there is a larger mini-graph called 'desk band' that can be displayed next to the clock:
Please see the bottom of the Graph page of the NetWorx User Manual for more details.