Tag editing seems to be sort of schizophrenic -- there are two places/ways to work with tags and they behave differently.
The Tag Action window seems to be the primary place to work with tags. But, the width of an editing field is constrained to remain within the Tag action window, which can be insufficient. This is helped a bit the behavior of opening the slightly-wider field below the label, but still, the nav/tree/action column width determines the max tag field width, yet they have different purposes. It can be quite difficult to work with longish comments, names, artists, etc. Of course, the user can widen this column, but an appropriate width for tree navigation is very different from the ideal width for tag editing. Tying them together is the root of the current "problem"
In contrast, editing a tag in a view column can open a field much wider, apparently up to the width of the longest value of that field in the current view, limited by the width of the view to the right of the field. This can be quite large, MUCH larger than in the Tag Action window. However, a column in the right area of the view opened for editing can be squeezed quite small. And opening a list associated with a field can be clunky depending on the position of the selected field column/row in the view. Plus, tag edtiing in a view is limited to fields/columns that are shown in the view, while the Tag Action window can provide access to any or all tags.
Several alternatives, suggested here and in prior threads, would help this. A larger Tag action window is the basic need. It could be the existing window, detachable/floatable and resizable, with MC remembering this (sticky) so it can be closed/opened/closed/opened consistently. And/or, the Tag Action window could have an option to auto-zoom to a larger width and height. (For example, I requested medium-tall, which could be even better if combined with multi-line display of longer field contents)
The idea to show all fields of a record on a separate tab would be a nice option, but not as the only mode because many times I want to see other rows of the view while editing, to remind of related record settings and to help make tags consistent across records.
The need to also see other data in the view is why a detachable/floatable/resizable sticky-position Tag Action window seems to be the ideal solution.
Various photo/video/layout tools, such as Photoshop, InDesign, QuarkXpress and similar have the same need -- lots of property/editing boxes, configurable by the user. Some products let the user set up desired property/editing windows and positions, then save that configuration. Then set up another set of windows, sizes, locations, and save that configuration. Etc. Then the user can open the desired layout based on the current task. This could really be wonderful in MC because it handles the spectrum of media types. The optimum properties/tool boxes layout for working with music might be very different from working with photos, with videos, etc.