As someone who has been drawing a ton of sidewalks and crossings lately, this is probably the most annoying thing I have to encounter. You can get around the warnings for marked crossings that are automatically created by just setting the markings, but you don't have that option for unmarked crossings so you either have to set the tag in bulk at the end or hit the upgrade tags button on every node.
This has to be an easy fix to send in a pull request... 🤔
By "in bulk" do you mean the constance clicking back and forth between the right and left panes to upgrade each one individually?
As a JOSM user, who has only used iD occasionally, what does this "upgrade" do?
It adds
crossing:markings=no, which I feel like an unmarked crossing should have by default.
