You can use the Bootstrap classes .btn-lg, .btn-sm, or .btn-xs to easily change the size of a button. This can be done by adding the class ‘btn-lg’ (or one of the other two classes) to the class property of the button.
If the default sizes do not suffice, you can apply custom styling to make the button appear exactly as you want. Please see the documentation for further info on this.
As a quick solution to set fixed dimensions on just one button, you could also just set the Style property of the button in the Modeler to something like this:
height: 200px; width: 250px;
If you want the same style to be applied to more buttons then I think it's better to create a class for that.
Thanks Axel, that’s exactly what I am looking for