Is there a way to make a simple directional arrow to show the shift to/from sul tasto over time? As in this common notational convention:
Welcome to the forum, akhet. There’s no automatic way to do this at present, but it’s something that we certainly plan to add in future. For the time being you might consider adding the arrow using a text item and a font like this one.
Thanks for the help; I gave this a shot and the arrow doesn’t really line up with the articulation text since I’m selecting the sul tasto from the articulations menu, it generally is quite a bit higher. Is there a way to manually adjust its placement in the score so that it appears on the same general line after the “sul tasto” text? Do I just need to type sul tasto and use the arrow all as one text item?
You should be able to adjust the vertical position of both items in Engrave mode. I recommend you activate the ‘Avoids collisions’ property for the arrow text item and switch it off, so that the arrow doesn’t interfere with the placement of other items.
Hi, sorry to drop in on the subject. Has a different or more effective method been added in the upgrades since the last comment? Thanks!
In the meantime, the link in the OP has turned into outright spam. If this was a new thread, I’d flag it. 
To answer @Paul_Rubinstein : Dorico has quite advanced tools now to create lines, including arrows etc. See here in the manual.