I’ve created a custom gesture tool as outlined in A new custom tool — Bokeh 2.3.3 Documentation . In order to get some additional input from the user to guide the operation of the tool, I would like to trigger a dialog window whenever the tool is activated from the toolbar. I was wondering how I can respond to this ‘event’. The only Event in bokeh.events that seems to respond to activating a tool in the toolbar seems to be bokeh.events.Reset. It is not clear to me how I might add a similar event myself to the activation of a custom gesture tool.