Nope, this is not possible, multi-edit operations on form fields would be a nice addition, perhaps add it to the ideas topic?
there is no way to change multiple fields at the same time in the business modeler. i get around these kinds of issues by using conditional visibility. you can do the same by creating a duplicate row and have one row set with default and the other row set as never. you will then want to add a boolean to the object in question and set the the value true to show one row and the value false to show one row. then you would want to create a microflow that will retrieve all objects or a subset of the objects that you want changed and toggle that boolean. this way you can switch between default and never with the click of a button. hope this helps.