Is it possible to set a default gradient colour and opacity? I did try setting it in the template with no luck. Thanks for your help.

Maybe this will help you. https://inkscape.org/forums/beyond/gradients-pre-made/

I'm also want to change colour to olive green

Paddy - I think I must be missing something. What I'd like to do is this:

* open Inkscape

* draw a rectangle

* choose Gradient for that rectangle

* that rectangle would then be filled with a default gradient

I created a Gradient swatch, then updated the template, but couldn't see a way to make it the default gradient fill.

Here's why I'm asking: currently every time I create a gradient I have to turn up the opacity from 0 to 255 for one colour, then change both colours. The gradient swatch takes away one step, but ideally it would take away both steps. Any ideas?

There´s no way to make a default gradient on your own. 

I would suggest making a new template incl Objects with applied gradients and Copy+Paste-Style them to new objects.

Polygon - Thank you for your help, I'll do that. Fingers crossed this feature is included in later builds.