I think it's high time we require an autosave system or a warning notification while accidentally exiting a proposal writing.
I have noticed there is an autosave system in Thread writing/posting in Upwork community. But it's a matter of great regret that there is no autosave system, or not even a warning notification while I exit the windows or close the proposal writing by accident. I am suffering a lot when I accidentally closing the windows, since I have to write the proposal over again, including adding Milestones estimation (in fixed priced project) and proposal writing.
I hope Upwork will notice this and try to solve this problem professionally.
Abu Saleh Ridoy.
Don't wait for Upwork to make that change.
Write all your proposals in Microsoft Word or a free version from a competitor and then cut-and-paste into Upwork when you're ready.