Ability to add checkboxes to a "Run customised build" dialog

It would be great if I could add checkboxes to a "Run customised build" dialog.
If I check it, for example, the variable will be set to "true", otherwise it is left as "false".

I could use a custom variable for that, but this would be not intuitive and explicit for users.
There are many variables in my project including user-defined and service variables (not needed for users).
In that way the list of available variables becomes confusing for everyone because It combines more and less important variables just in one place.
Eventually I have to explain which variables are editable and what they are meant for and good naming doesn't help much.

So I want users to understand what they can and should customise by looking at the "Run customised build" dialog.

Under the hood those checkboxes could be made just as same build variables with a corresponding true or false value.