Hey!
If you are working on two or more extended monitors, try right-click on Construction Tab tree structure elements on MAIN SYSTEM MONITOR (nr. 1) , before drag Assembly Properties window here (to MAIN SYSTEM MONITOR, where windows start button is). I had this problem too, and find this solution.
I would have never found this solution, thank you for suggesting this additional solve! 9 years later with COVID-19 and everyone working from home and laptops, this happens so much more frequently.
Here is where it got strange though, I have 3 monitors.
Laptop screen - The right-click works
DVI-D to HDMI connected monitor - The right-click works
HDMI to HDMI connected monitor - The right-click doesn't work (Tried with and without a USB-C hub)
For me it seems to be either monitor or connector dependent for secondary monitors.
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