You can input hammer-ons/pull-offs on any notes belonging to fretted instruments using the ornaments popover, both during note input and by adding them to existing notes. If you select multiple notes, Dorico Pro automatically inputs the appropriate slurs. You can also add tapping with hammer-ons/pull-offs to existing notes.
Procedure
Result
The hammer-on/pull-off you specify is input on the selected notes. During note input, this is usually the last note you input.
If you selected multiple adjacent notes assigned to the same string, Dorico Pro automatically inputs slurs spanning the selected notes and centers hammer-on/pull-off indications on the slurs. For slurs with multiple hammer-on/pull-off indications, each indication is centered over the range of notes in the corresponding direction. You can choose to show hammer-on/pull-off indications on each note on the Guitar Techniques page in Engraving Options.
By default, hammer-ons/pull-offs appear on both notation staves and tablature and are placed above the staff.
You can also add hammer-ons/pull-offs to existing notes by selecting them, activating Technique in the Guitar Techniques group of the Properties panel, and selecting the appropriate indication from the menu. To show hammer-on/pull-off indications centered on slurs, select all notes except the first note under each slur.