Open Impress, run Tools-Presentation minimizer. In step 5. choose "Duplicate presentation.." Press Finish to be offered Save dialog. See that presentation minimizer offers to save in current directory, instead of LO default defined in Tools-Options-LO-Paths (or previous saved).
This may not be bug at all. So far, I see it in Linux with bibisect and not with Linux installed (opens user's home) and not with Windows installed (opens last used). So I close.