Schedules stay on your device — opening a file never uploads anything.
Save writes back to the file you opened (Chromium browsers); otherwise it downloads a .json. Nothing leaves your device.
“Save as…” lets you choose a new name/location — that copy becomes your working file. “Download a copy” exports the .json without changing your current file.
Tip: in the print dialog, keep Background graphics on so bar colours and shading come through.
Shares the actual project .json so the recipient can open and edit it — not a review copy. Nothing is uploaded: it goes through your device’s share sheet, or downloads if sharing isn’t available.