Use tabs by default
Okular has had tabbed document features for years, but defaulted to turning the feature off. Having it on is overall a better default, for what I believe to be the following reasons:
- It's more common for document-based apps like Okular to be tabbed these days than for them to not be; it would therefore better match user expectations.
- Tabbing helps the casual/novice user keep their workspace organized better by having fewer windows open at the same time. This kind of usercan quickly become overwhelmed when they have too many windows open.
- Tabbing better accommodates the usecases of advanced/heavy users who will open many documents, by making it easier to switch between open documents.
- Off-by-default features are generally considered poor practice today by the VDG, especially for fairly basic functionality like tabbing. See https://community.kde.org/Get_Involved/Design/Lessons_Learned#New_off-by-default_features