When watching younger people use Piwik I noticed how it is actually expected that values are saved immediately. In this case we had a look at the "personal settings" page and it was not clear that a save button needs to be pressed, instead it was waiting to see some kind of feedback once a value was changed (different value in select field selected, when leaving a text field, ...). This is also often the behaviour on mobile apps so people seem to get used to it and almost expect it to be like this on desktop / websites.
It would be nice to add some point actually save values immediately after a value was changed. We would then eg show "saved. undo" next to the field. The "undo" field would be clickable and would undo the last change. See feature provide undo feature for manage entity screens.
Could be done as part of the "Manage entity component" in https://github.com/piwik/piwik/issues/6951