Once set, always set.
I have to delete the technique from the list of mappings, and add a new one.
I don’t think it does anything yet, so don’t worry about it.
Once it’s implemented it could work something like this (though it could be slightly different, but the concept should end up being similar):
Just as a side (unoffical) tip for advanced users who are comfortable working with an XML Editor.
Disclaimer: These are personal hacks only meant for someone who understands and works with XML…experiment at your own risk. If you don’t already have a favorite XML editor and know your way around it, this probably is NOT the post for you.
If I’m working with a huge list of techniques, I often do it in XML pad. This way I can easily change the order of things, copy and paste things from one field to another, etc. It makes it easier to cross examine parameter relationships between different Techniques, etc.
One example of where this REALLY comes in handy…
Imagine you’ve already got a ton of techniques, and you want to duplicate a set of them then add the +mute technique.
I could open two copies (or you can do it all in the same copy if your XML editor is advanced enough to limit search/replaces routines to specific blocks) of the same doricolib file, run a couple of search and replace routines to change the in the scratch copy, then block copy and paste it all into the working copy. Now I’ve made a template for all my muted strings in a few key-strokes, as opposed to having to duplicate/tweak them all ONE BY ONE using mouse clicks and pop-up entries in Dorico. I can just use the 10key to go down the template by column and make my key-switch changes and other tweaks.
Next I’d do the same for 'vibrato, non-vibrato, etc."
A task that would take hours in the native Dorico map editor reduced to less than 2 minutes 
Note that eventually we’ll get exclusion groups, working fall-back techniques, flags to choose latching vs non-latching techniques, and so many entries for all of our potential technique combos might not be necessary anymore. Meanwhile, this works well, and it should keep working in the future unless they decide to make some pretty radical changes to how Dorico makes his technique decisions.
The safest way to go about this without accidentally breaking default project settings is to go to the Expression Map editor, hold ctrl and select all of the expression maps you want to ‘export’ into a single doricolib file, then ‘export’ the expression map. Now you can experiment with editing that file in an xml editor and re-import it when you’re done. While the file is named with a *.doricolib" extension, it is actually <?xml version="1.0" encoding="utf-8"?>.
I usually just work with a single Expressionmap at a time, this way it’s easier to manage the duplicates in my main list as I import them back in. So, if you try to import a map that has the same as a map already in your loaded list, Dorico will add an extension to that id…and you’ll see extra copies added to your list of maps. That way you can easily swap around between different revisions in the Play tab, and eventually get rid of the ones you do not want anymore.
Before trying anything like this I do recommend saving a version of your Score/project in a safe backup location ‘before’ loading any maps that you tweak in this manner. That’ll give you a fallback just in case you botch something terribly and save the score after the botch. When ever you save a score all of your expression maps get zipped up in the Dorico Project in this exact same format (add a zip extension to a dorico file name and have a look inside for yourself), so that’s why I recommend keeping a back-up copy, and only working with exported/imported maps until you are confident things are solid enough to carry over into the default slate of expression maps.
Once you’ve confirmed your map imported, works as intended, didn’t break anything you can save it all in your own score templates so you don’t have to re-import custom maps with every new project. If you want to make all of your imported expression maps part of Dorico’s defaults it’s possible to merge your stuff into the “ExpressionMapsDefinitions.xml” file located in Dorico’s home installation directory (make a backup of the original first so you can always start fresh if necessary, and be aware the Dorico updates/upgrades could overwrite it at some point). (Actually, it seems like one might be able to replace the “ExpressionMapsDefinitions.xml” map with one directly exported…I’ve not tired it yet, but this theory is based on the assumption Dorico ‘ignores’ the fields it doesn’t need when parsing things from this file, and just grabs the stuff between the tags. If you try it, be sure to export ALL of the expression maps, including all the default Sonic SE stuff that came with Dorico).
When I’m unsure of , I’ll add it to a map in Dorico’s native expression map editor first, then export it so I can have a look.
I didn’t realize that the expression map files are just XML. Thanks for another great tip, Brian! Yeah, I’ll be editing the maps in Notepad++ from now on.