One missing feature from the Proton Suite is a Time-tracking layer integrated in the Calendar app.

It would be a handy feature to toogle on/off alongside your planned schedule, in order to track the real time invested in your projects, get records and overviews, and be able to learn from them and improve your workflow. All with the same level of privacy and encryption of the other features.

Right now Proton users still depend on external apps to track their time, which don't integrate in the Proton ecosystem nor offer the same kind of data security. More on the contrary, multiplatform time-tracking sync apps are full of commercial trackers (pun very much intended) alongside security bugs.

Also, If the Calendar app is indeed planning to allow to run it locally and asynchronized as an option, the Time-tracking layer could work the same way for those who don't want/need online sync between devices.

I think there's a niche in the market for such (encrypted) feature, and it would be a point of attention for (small) businesses and independent entrepreneurs, while weighting on the idea of the Proton Suite above others.