Being able to add sections allow to store e.g. a second password, several serial numbers, several IBAN number etc. that belongs to an entry. This can be relevant for a login where a second password. is necessary. or a login associated to a bank account and a mobile account, where I don't have a separate entry but I want to keep things together.

Organizing the information in sections makes this really easy to grasp (UX, overview) and also possible to collect different types of information about one thing (multi-usefulness).

Interestingly enough 'add section' already exists with the "Identity" type of entry, but not for other entries. Quite odd, but that means it would be really easy to add for the Proton Developpers. The functionality exists, it just needs to be expanded to other entries.

In 1Password all types of entries are able to add sections. When bringing them over into Proton Pass, some sections disappear (which is really annoying because sometimes the section title is relevant for the text or hidden entry that follows). So this is another useful use case for sections: happy migration.