hiding visibility toggle button if detail is null

I've found several posts on how to hide rows that are null, but I'd like to remove the vibility toggle if the row is null.
Currently, in the detail group Visibility settings, I have it set to expression, using =iif(Fields!tagName.Value="",true, false) and the checkbox in the Visibility can be toggled by another report item and I have one chosen.  It works great.

I'd just like to hide the toggle button if that value is "", and if it's possible, change the toggle from a plus to a minus so the ones that have values have minus signs.  If they want to close them up, they hit the minus.  Right now it's confusing because they're all +.

Possible?