To confirm, I don't think there's any real belief in the party or the wider independence movement that Scotland would somehow 'inherit' the UK's EU membership. The idea seems to rather be along the lines of negotiating fast-track entry into the EU. It's possible that this won't happen, but on the other hand it's worth noting that Scotland is already subject to EU rules and compliance is a much less complex issue that for a country which is entirely outside the EU.