Two new buttons have appeared on my main toolbar (the one that is called toolbar). They have no associated description when the mouse is hovered and neither appears to do anything. If I go into Dopus Customise mode, I see that they appear in the spot where a placeholder that "Marks the place in the toolbar where Namespace-specific toolbar buttons are to be displayed" is defined.
What are Namespace-specific toolbar buttons and how do I get rid of them? (assuming they do not serve some vital purpose)
Namespace items on a toolbar or menu are dynamic commands placed by Windows or programs external to DOpus that only apply to certain "not really a folder but it looks like a folder" locations. Such as the Desktop, My Computer, or the Control Panel. When you switch to a standard folder, the namespace items disappear, when you come back to My Computer, there they are again.
If you want to get rid of them, in customize mode just remove the namepsace marker on the toolbar or menu they're in.
I don't use namepsace items myself, but they're available for those who want them.
Is there a way of establishing which "Windows or programs external to DOpus" put them there and what they are supposed to be for? As you suggest I can simply remove the namespace marker but I'd be more comfortable doing that if/when I know what I'll be foregoing.
They generally just come from whichever namespace you are currently viewing.
If you open Explorer and browse to the same folder you will generally see the same buttons. For example, Explorer adds 'Move To' and 'Copy To' buttons to a lot of its "real" folders. However since the desktop is generally the only "real" folder that Opus displays as a "virtual" folder then in Opus these buttons will only appear for the desktop.