I for one would LOVE the ability to move around a set of actions. I recently renamed a lot of functions external to mp3tag and when i got back into mp3tag all of the .mtg or saved selections no longer applied.
Might be a lot simpler to rename your actions into subcategories and if necessary duplicate them. The way mp3tag saves the position of the action is by the order in which it is read, so if you rename it externally (in the appdata folder) the next time mp3tag loads it reloads that file. If anything, to piggy back on your request here, it might be easier if we had the ability to click a subcategory and run all actions therein. The save selection feature is nice but you have to order them manually and it can screw up scripts if they're dependant on one another (standardize strings, run regexp, glory... then you realize the standarize function was run after the regexp and everything failed.)
My suggestion here for you would be to edit the action fields manually. Play with them in mp3tag and arrange them how you want it in a single action file. Then go to the .mta file in the appdata folder copy out the code you want and replicate it across whatever actions you want.
After a while of looking at these action files even if you're not that experienced in coding you'll be able to realize where your desired function is and play around with it. I find this essential
when editing complex actions as often times I need to duplicate the functionality (especially where recursion is involved) and using their action panel setup is unwieldy. You'll become a pro in no time with doing this and you can standardize your code across any set of actions you want. A program like notepad++ is great as you can use find/replace across all open documents and locate the code you wrote rather than try to remember where it was.