[Ayman]

One of the ways to do it is with CSS.
You need first to find the class of the target button and then hide it with something like

.class-button{
         display:none;
}

[Ayman]

I have never tried to use “BuddyDev bp multinetwork” but as you described your problem it looks like it has something to do with “BuddyDev bp multinetwork” and not BuddyPress it self. To be more specific I think you should recheck your domain mapping settings.