For people with large databases many operations seem to be single threaded and cause the application to become non-responsive. Some of these operations may run for literally days, and the user either has to wait or force quit and the remaining user controls are locked out.
This bug exists both on Mac and Windows where button clicks are not recognized for long running operations. On the GEDCOM export, Drag N Drop, and Citation merge any attempt to cancel is ignored. On all three, in both environments, using the Cancel button does nothing, and the only way to stop the operation is for Force Quit the application.
Clearly some optimization is needed on these operations, and multi-threading is needed so user controls operate and force quits aren’t necessary.