Tree navigation is now created on demand, meaning that SPDX documents are only processed when the user is really interested and clicks them. This speeds up considerably the initial load time (especially when the SPDX archive is big). Drawbacks is that we can't conduct a search with this kind of information in memory and that we don't (immediately) see more details from the treeview just by navigating.
In either case, current result is quite usable. More improvements to follow in next commits.