how to change motor spin directions?

Yes. that's an idea! However, I should know why the float spinbox wouldn't take a negative number. I tried:

setp stepgen.0.velocity-cmd -2

and it worked to reverse direction. I should read up GladeVCP how to set range.

Thank you!

To set up a spin-button you have to have an Adjustment widget associated with the spin-button and that is where you set the range of values that can be output by the spin-button.

So if you are using an existing example Gladevcp you will need to open it in the Glade editor, open the adjustment widget associated with your spin-button, and change the minimum value there to a negative number (instead of the default of 0).