Proposal:
Make the sidebar of the web view manually collapsable.

Details:
This proposal is only about the function collapsing sidebar itself. This proposal is not about how this feature would be implemented on the UI.

Related Threads:

[1] Option to collapse sidebar
Link: https://protonmail.uservoice.com/forums/945460-general-ideas/suggestions/48123095-option-to-collapse-sidebar
Note: The idea of collapsing is the same. However the author did also mention a concrete UI implementation in his idea, which might make voting difficult.