In guitar music it’s sometimes helpful to place a left hand finger on the string in readiness, before it actually needs to play. Sometimes it will be on the fret where it is about to play, sometimes on the same string but a different fret. This sort of thing isn’t usually indicated in printed music, but I tend to pencil in some sort of reminder to myself. Is it possible to insert something similar in Dorico? I don’t mind whether it would appear in a printout, as long as it appears on the screen.
I don’t think it’s natively possible, but if you can show us an example of how it should look like we can recommend the best way for you to achieve your goal.
If the staff isn’t too cluttered I might pencil in a notehead in brackets, like this.
Or I might just put the fingering in at the appropriate spot, without a notehead. It doesn’t really matter what it looks like, as long as it serves to remind me to put the finger down in good time.
Similarly I will often pencil in a reminder to damp an open string, usually with a little “x” opposite the original note. There is an example of this in the photo too. I don’t know whether this is feasible in Dorico either.