I was searching for a way to get the convenient archive mounting found in nautilus, and wound up making an annoying script with the package "archivemount" which did the trick. Little did I know, Dolphin has this option in Preferences > Navigation > "Open archives as folder". Great! (Should be default IMHO) Anyway, the automount seems to be read-only for some reason. There is no technical reason it needs to be read-only - mounting archives as a writable filesystem works just fine with archivemount - so this decision is rather arbitrary, which is why I've classed it a bug rather than feature request. I can think of some plausible social and psychological reasons why mounting read-only might be a good default, but that doesn't mean full access shouldn't be possible even as an option.
Hi, Dolphin uses kio slaves to access archives, and they don't currently provide read-write support (see for example https://bugs.kde.org/show_bug.cgi?id=77127). That said, integration with archivemount is something that could be considered.
The current default in Dolphin is to open archives with Ark, which allows read/write access With "Open archives as folder", I can confirm it still opens the folder as read-only in Dolphin 24.12.1 I'll let the current Dolphin maintainers evaluate this.