It would be great to be able to copy and paste individual blocks from one preset to another.
A more ergonomic interpretation of this idea has already been suggested here Load block from preset
And one more idea for copying the whole chain here Copying complex signal chains between scenes/presets
both good ideas, but from a programming perspective adding a copy/paste function in the 3 dot drop down menu seems like a pretty easy add.
I actually prefer this request to the one you consider “more ergonomic” as it would work across scenes. I find the current link / unlink behavior of parameters to be fairly awkward when setting up new scenes and this feature better addresses that.
I agree that copying between scenes will be easier through copy\paste. Thus, both options are needed, since this is actually a variant of templates stored in presets. You yourself said that the copy\paste method is fraught with inconvenience and the risk of losing changes during the switching process