Unmarking stockpiles, zones, burrows, etc sits, as it should, under the route to marking these. It's often logically going to be useful to paint/unpaint under the respective-to-type menu. All these things are essentially 'invisible' to the dwarfs, until their designation causes an effect (items brought to the nominal stockpile), but are totally different things, and not all visible to they player stockpile areas are, but the others reveal only when activating the respective exiting method, I'm half sure). Could you have a generic "clear all" apply across that whole board of differing intangibles? If you do, keep the in-function this-thing-only unpainting method, definitely (perhaps slightly more consistently) or you'd have to dip in and out of the emplacement mode to unemplace any changes of mind.
Removing (dug) stairs and ramps is an option within the submenu where such things are dig-created. You used a pick to make a (relatively) undug cell into your ramp or stair and then you must again to remove the bits you asked to remain. Ditto with dug-then-smoothed-then-carved fortifications that you want to open into full empty. It ought to stay there (so long as you don't dig the 'full dig-out option to a nearer branch of selection) because of functionality, though obviously it' s not a "stay there to correct the designation, which is just overwriting with a plain-dig (or channel or whatever) before you exit. Staying there or coming back and stopping a designation (that hasn't been fulfilled yet) being a designation is also under that designation menu. But with designations being another invisible-to-dwarf' psychic' marker, the same argument as for the removal of (the totally different) invisible application of the will-of-the-fortress should apply, maybe. A "clear all", though there's key differences.
Removing built things is not the same. For cancelling their building before they are completed (or started) it's the q-interface upon thei 'ghost marker' and cancel them, individually. Once built, it diverges. Constructions need the Designation of Remove Construction, which you might think odd, while Workshops and Furniture-items get an in-workshop option to dismantle. There are any number of arguments for and against, but I suspect the prime mover is that anything that has an entry as a Room has that extra interface (e.g. for who it applies to, if not also including the orders part of a workshop) while a wall just has no need for this representation, so was never given it. Maybe ideally it should still be given (perhaps by 'adopted child' membership of the rest of the built-things list, just not listed in the Room list because that already gets full up with all the things that do end up on that) a q-menu access to a Dismantle option to replace Designate-Remove. Though they have in other ways some similarity to raw diggable rock, even if they aren't diggable.
The question is, though whether a grand "cancel this" commamd, of whatever form, should act on everything removable. To what extent? Just every type of zone, stockpile and burrow designation? Should it include construction dismantling (dangerous!) in with that? Technically would some people expect it to also convey Designate Dig on natural rock (and felling trees), or does it act like deDesignating upon any/all proper Designations (including Dig, i.e. it undoes a previously requesyed Dig and even Mark-Only Dig) or is it asked to serve the equivalent of the Ramp Removal option? Does it also de-define room-spaces defined from Furniture, and would it do that with or without asking for the unbuilding of that Furniture at the same time?
There's a lot to be considered. By whoever is going to be asked to consider this (maybe the new partners are providing suggestions likw this. I expect it's already on their mind, but don't know how quickly it could come to fruition, or in what form.