Assuming you want each of the 3 different press types of the physical button (single, double, hold) to trigger distinct actions of physical Alexa devices (ie, devices that cant be controlled directly from SmartThings), then you are correct. You will need to create 3 separate virtual “Alexa” (door contact sensor) switches.
I used Alexa ROUTINES to trigger Alexa actions (eg, turning a Kasa outlet on or off) from my virtual switch – though I have yet to create multiple virtual switches.
I selected “Add action” to choose the desired resulting action.
I was able to select my virtual switch as a trigger for the desired action by pressing “When this happens” and then pressing the “Device” icon.
I couldnt find a toggle function in the Alexa app, so I needed 2 routines (one for ON and another for OFF).
But the desired action occurs not only when I press the physical button, but also when I toggle the virtual switch directly from the Alexa app.
I would assume this would work for multiple virtual switches, but I have yet to create more than one.
Hope this helps.