Hi Andreas, select the notes you want to connect and type the letter s. If you want to add the letters p or h you will have to use text as far as I know. Are you talking about notation or/and tablature?
I think you can use P and H from somewhere in the properties panel, guitar techniques or something…
To the team: You could consider enabling automatic H and P placement for fretted instruments, depending on the melody going up or down. As you know, these “techniques” aren’t really that, but rather two of the three ways of playing legato on a guitar…