If this script already exists, then I don't know what terminology it's being identified by in order to search for it. Otherwise, I've been striving to convert two importantly and inexplicably neglected VX Ace scripts into MV plugins, but as learning Ruby and JavaScript is not as easy for me as it is for other people, it's been slow going. These two scripts bear functionality which are extremely similar in fashion.
Chaining SkillsIn this context, chaining skills refers to creating a skill which can allow the user to instantly use another skill on his or her turn in battle, selecting from
multiple available choices. This is based upon the YEARepo script,
Active Chain Skills.
In battle, the user selects a skill which has been given a note tag referencing other skill IDs to which it can be chained (and these in turn can be chained to still more skills). When he or she uses this skill during battle, a prompt comes up for multiple learned chain-able skills and their corresponding buttons. When one of these buttons is pressed, its corresponding skill is used as soon as the present skill finishes playing out. It's actually much simpler than it sounds in practice.
For example, a grapple skill could be chained to one of various throws.
Combo SkillsIn this context, combo-ing skills refers to creating a skill which can allow the user to input a string of buttons while using a skill on his or her turn in battle which will unleash
a prompted series of other skills from multiple available choices, which the possibility of certain combinations activating a finisher. This is based upon the YEARepo script,
Input Combo Skills.
In battle, the user selects a skill which has been given a note tag referencing other skill IDs which can form a combination of skills. While the skill is playing out, the player presses whatever combination of buttons corresponding to a prompt of multiple learned skills to play out that series of (traditionally five) skills one after another. As a bonus, a specific combination can be set to activate a finishing move at the end of the sequence. It's actually much simpler than it sounds in practice.
For example, a series of karate moves could be combo-ed together in quick succession.
Since I'm not the best at explanations, I recommend that people try the two VX Ace scripts found at the links cited above to develop a clearer understanding of this game play mechanic.