I haven't come across any options to add a function ie. "spoiler" tag to the forum editor? Is this possible?

Thanks. 

1. Go into the ACP
2. Customisation -> (Editor) Toolbars
3. Drag the spoiler button from the 'Buttons not on editor' toolbar to the 'Editor' toolbar

Aha TY. ; )

 

And how can we add a "add image from url" button to toolbar?

37 minutes ago, andavis said:

And how can we add a "add image from url" button to toolbar?

If you paste the url it will add the image