What area of ethics appraises the value of moral actions? I was wondering if there was an area of ethics that does that, but after some research I couldn't find anything on that matter. Is there any such area?
First for moral skeptics there's no such value of moral action in general, only one's temperament or feeling towards a moral action according to wiki reference here:
Moral skepticism (or moral scepticism) is a class of metaethical theories in which all members entail that no one has any moral knowledge. Many moral skeptics also make the stronger, modal claim that moral knowledge is impossible. Moral skepticism is particularly against moral realism which holds the view that there are knowable and objective moral truths... Some proponents of moral skepticism include Pyrrho, Aenesidemus, Sextus Empiricus, David Hume, Max Stirner, Friedrich Nietzsche, and J.L. Mackie.
For moral realists, the area value can be appraised is one's preferred or strictly adopted normative ethics, mainly includes virtue, consequentialism, deontology.
Virtue ethics describes the character of a moral agent as a driving force for ethical behavior, and it is used to describe the ethics of early Greek philosophers such as Socrates and Aristotle, and ancient Indian philosophers such as Valluvar. Socrates (469–399 BC) was one of the first Greek philosophers to encourage both scholars and the common citizen to turn their attention from the outside world to the condition of humankind.
One way to divide various consequentialisms is by the many types of consequences that are taken to matter most, that is, which consequences count as good states of affairs. According to utilitarianism, a good action is one that results in an increase and positive effect, and the best action is one that results in that effect for the greatest number. Closely related is eudaimonic consequentialism, according to which a full, flourishing life, which may or may not be the same as enjoying a great deal of pleasure, is the ultimate aim. Similarly, one might adopt an aesthetic consequentialism, in which the ultimate aim is to produce beauty. However, one might fix on non-psychological goods as the relevant effect. Thus, one might pursue an increase in material equality or political liberty instead of something like the more ephemeral "pleasure".
First, Kant argues that to act in the morally right way, people must act from duty (Pflicht). Second, Kant argued that it was not the consequences of actions that make them right or wrong but the motives of the person who carries out the action... Kant's argument that to act in the morally right way one must act purely from duty begins with an argument that the highest good must be both good in itself and good without qualification. Something is "good in itself" when it is intrinsically good, and "good without qualification", when the addition of that thing never makes a situation ethically worse. Kant then argues that those things that are usually thought to be good, such as intelligence, perseverance and pleasure, fail to be either intrinsically good or good without qualification. Pleasure, for example, appears not to be good without qualification, because when people take pleasure in watching someone suffer, this seems to make the situation ethically worse.
In short depending on your normative position, moral value can be appraised based on one's virtue characters, or some quantifiable utility measuring "happiness"/"usefulness"/"surplus", or the goodness beauty and taste of one's motives and wills in awe of the sublime behind a certain moral action.