The Juicebox Plugin for Lightroom does not support a traditional 'preset' file (as used by JuiceboxBuilder) but you can create a 'template' in Lightroom which can be loaded at any time to apply a certain combination of configuration options to a gallery. (This will save you from having to set each configuration option individually.)

With the settings as you want to save them (in the Lightroom plugin's interface), click the + sign to the right of the text 'Template Browser' (in the left panel of the 'Web' section) and select a name for your template.
At any time in the future, if you want to apply these settings to a new gallery, just expand the 'Template Browser' control panel, scroll down to the 'User Templates' section and select your template.