Toolbar buttons integrations (along with the other integration types) can only be modified if you have a copy Formativ Creator or Studio. In this case you would select the appropriate applet in the designer and turn off the toolbar integrations.
If you only have a copy of Runtime the buttons cannot be easily changed. You could have a look at the header of the applet file (it’s an XML file) to see where the buttons are defined and edit it manually. Of course, this approach is totally unsupported and not encouraged.