Sync Timing - Preset specific time, date, frequency to sync files & folders to ProtonDrive
What is missing and to make things infinitely easier is not only syncing which is CRITICAL, but to have functionality to set the frequency... continual on changes, specific days, daily, weekly, monthly, semi annual along with the time to do so. This could be extended to be a single upload to regular on the specified intervals. Given that a file size can be 200GB (full system back up for example) picking a time and date to upload such a file is important due to the time and bandwidth that this would take.
This along with unlimited file size will differentiate you to the market leader in secure cloud storage, Tresorit. It will also make it far more impactful than it currently is.
I'm a Business Tresorit user as well as a Business Proton user and have been from the start with both.... Tresorit is miles in front of Proton Drive and this should be expected given this is new for Proton. However, I believe that syncing and the functionality suggested in this recommendation will help your push for subscribers greatly