I know the use of the sidebar for navigating betwen files is frowned upon but I generally have two or three related but separate projects open at the same time and each one of these has between 50 and 100 or possibly more files. I rely heavilly on being able to view my prject tree in the sidebar. Problem is, sometimes when launching ST the sidebar does not work properly, i see my top level directory tree for the project but none of the subdirs will expand.
The only way I have found that will fix this issue is to delete the project files and recreate them. Sometimes, when creating a project the new project suffers this same problem and the only thing I can do is delete the project files and recreate them. I have on occasion given up trying to get a sane sidebar which basically boils down to not being able to work on that project till I come back to it later to again attempt to create a project with a working sidebar.