I get the time to look at it, and this is the thing I should have checked first, but either in a GeDialog with a Layout created in a script, I'm not able to hide a tab.
Since you said it was working previously, could you confirm you don't want to hide only the content (in your case the 3 StaticText) but also the tab in the tab entry, isn't? If yes could you provide a code sample because I would say even in a normal case I'm not able to reproduce.

import c4d

class Dlg(c4d.gui.GeDialog):
    def CreateLayout(self):
        
        if self.TabGroupBegin(10001, c4d.BFH_SCALEFIT | c4d.BFV_SCALEFIT, tabtype=c4d.TAB_TABS):
            
            if self.GroupBegin(10010, c4d.BFH_SCALEFIT | c4d.BFV_SCALEFIT, 0, title="First Tab"):
                self.AddStaticText(10011, c4d.BFH_SCALEFIT | c4d.BFV_SCALEFIT, name="Text01")
                self.GroupEnd()
                
            if self.GroupBegin(10020, c4d.BFH_SCALEFIT | c4d.BFV_SCALEFIT, 0, title="Second Tab"):
                self.AddStaticText(10021, c4d.BFH_SCALEFIT | c4d.BFV_SCALEFIT, name="Text02")
                self.GroupEnd()

        self.GroupEnd()
        self.AddButton(10030, c4d.BFH_SCALEFIT | c4d.BFV_SCALEFIT, name="Remove First Tab")
        
        return True
    
    def Command(self, id, msg):
        if id == 10030:
            print self.HideElement(10010, True)
            print self.LayoutChanged(10001)
            
        return True
    
def main():
    global dlg
    dlg = Dlg()
    dlg.Open(c4d.DLG_TYPE_ASYNC)

# Execute main()
if __name__=='__main__':
    main()

To me, the only way to remove a tab is to flush the complete group master of the TabGroup and re-add tabs except for the one you don't want.

Cheers,
Maxime.

Regarding the problem, I have to dig into it more on Monday, but I guess this is due that LoadDialogResource actually creates a new dialog that is embedded within the original dialog, but of course, nothing you can change, so I have to see if it's a bug of something else missing

Cheers,
Maxime.

Maybe you have to call LayoutChanged() after that. See gedialog_gadgets.cpp.

Thanks for that example! However, in that code, hiding the group is done in Command(), so on user interaction. I need to hide it when the dialog is opened. The second (and probably most significant) difference is that it's a dialog which creates its complete layout in CreateLayout(). My dialog was like that before, and hiding the tab group worked just fine. But now I changed my dialog to load its layout from a .res file, and since then the group does not hide anymore.

So, the question remains: How do I hide a TAB in a TAB group defined in a .res file?

Bool SomeDialog::CreateLayout()
{
	if (!GeDialog::CreateLayout())
		return false;

	// load dialog from resource file
	if (!LoadDialogResource(DLG_SOMEDIALOG, nullptr, 0))
		return false;

	if (_showFirstTab)
	{
		SetTitle(GeLoadString(IDS_SOMETITLE));
	}
	else
	{
		SetTitle(GeLoadString(IDS_SOMEOTHERTITLE));
		HideElement(DLG_TAB_GROUP_0, true);
		LayoutChanged(DLG_TAB_GROUP);
	}
	return true;
}

I also tried LayoutChanged(DLG_TAB_GROUP_0) and LayoutChanged(DLG_SOMEDIALOG), with no effect whatsoever.

Cheers,
Frank