Hi:
Am testing SP Page Builder Pro Alpha v4.0.0-alpha.1 in a sub-directory at https://blackfire.com.au/lp/
When working on the [Home] page it shows the URL as https://blackfire.com.au/lp/index.php/component/sppagebuilder/?view=form&id=1&layout=edit&tmpl=component
However, when I click on [Preview] it links to https://blackfire.com.au/index.php?option=com_sppagebuilder&view=page&id=1 (i.e. ignores the /lp/ directory) and then redirects to the current website at https://www.blackfire.com.au/cms/ (as it redirects to there from https://blackfire.com.au/index.php)