Would it be possible for a developer to add in the ability to make a key command to add a border around some text or is it logistically infeasible?
Do you mean a key command do set this kind of setting?
It would probably need a script, where it would open the lower panel if not open, then mouse click at a specific (x,y) location on your screen (or look for specific text), to click the setting combinations you require (then perhaps close the lower panel) so you can continue.
AutoHotKey (Windows) or Keyboard Maestro (Mac) or similar should be able to do this. The last time I used Keyboard Maestro, I put it into record and it recorded mouse click locations etc. (I would think I would have done this with AutoHotKey also) so you do not necessarily need to know how to create the script. You can tidy up the recorded script if necessary. (It does not record timing, although if you ever need timing (to wait for something to happen before the next action, you can add it manually.)
Then assign your own key command to trigger the action.
This might be quicker than waiting for something similar to be added into the program itself, as far as I know it is not possible looking at the key commands.
Others here might have better suggestions.
Yes, I was just requesting that the developers (they check this don’t they?) could put that in the list of Key Command shortcuts you can make. Otherwise I REALLY appreciate what they’ve done with the customizable shortcuts (other than having to add one externally to bounce an audio file)
Yes the Dorico team view every post. 
Just to check, I quickly created it (Mac, Keyboard Maestro). I see some other ones I used for Dorico to automate things too.
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It is this fast. I had the text selected after inputting it, then did my key command. It ran my recording of what to do, open lower panel, click to turn on the box setting, close lower panel.
If you define a new paragraph style that includes a border, and save it as a default (not as the Default Text style, just as a user default), then you can assign a key command that will create staff or system text using that paragraph style.
You could also record a user macro to turn on the border property of selected text, and then invoke that macro from the menu or from the jump bar (or assign a key command, with a little manual effort). The user macro would look like this:
local app=DoApp.DoApp()
app:doCommand([[UI.InvokePropertyChangeValue?Type=kTextBorder&Value=null: ]])
I’ll give the paragraph style a shot thanks!
Thanks so much man! Had to make sure the new paragraph style started with A so it would be first in the list (so I could just hit command-option-` then 3x return), and then had to adjust the text size and the left/right border paddings.
Do it in the paragraph style, then you can use just a single key command to create text with this specific paragraph style.
If you save your new paragraph style as a user default by clicking the star button in the paragraph styles dialog, then you can assign a key command in Dorico (in Preferences) that automatically creates staff or system text using that style, so it doesn’t matter where it is in the list.