I knew I could count on you, Eureka! Thank you so much! Last command tested and work beautifully
Now I've just to play with it for a while to discover the best way to exploit it.
The simplest one could be to use it in a unconventional manner, i.e. for blocking user input on eips full screen prints (just invoke
lipc-set-prop com.lab126.pillow customDialog '{"name": "sample_custom_dialog", "clientParams": {"dismiss": true}}' before and after executing your eips script).
For example in Midori splash animation...
EDIT: It doesn't work well unless you manage to open a very little custom dialog, lets say 1x1 px... otherwise if the user clicks in the popup area it will appear cleaning the eipsed area
Then I'll see how to use it in a proper manner, as custom dialogs displayer