When switching to Engrave mode and using “Join”, the result is correct, but only if the long line is desired; alternatively it can be adjusted graphically, but my expectation would be that Dorico handles this automatically.
The direction of the slide indicates whether the shift is to a higher or lower fret, not whether it is to a higher or lower pitch. You may need to set the “String” property for the note to make Dorico aware of where you want the note to be played—it won’t assume that two notes played by the same finger are necessarily on the same string, and it will typically allocate each note to the lowest fret (and thus highest string) that it can.
(It can sometimes be useful to show the tablature for a guitar part, just to see what Dorico’s string allocation is doing. You can create a separate layout for this if you don’t want to interfere with the layout you’re going to print.)
However, I still do not quite understand why, for example, the e in bar 26 can be approached from above if it is interpreted as being on the 1st string. Technically it is possible, but it is not very common to slide onto an open string. In this situation Dorico should, in my opinion, recognise that there is already a note written on the e string, and if the slide is entered later or at the same time, it could adjust its “opinion” accordingly.
The pitch direction is essential in this case, as the OP also describes in his first post. I’ve been playing classical guitar for about 45 years and I’ve never come across this kind of thinking before. It doesn’t make sense.
Is it not ‘down’ to a lower fret and ‘up’ to a higher fret, i. e. down referring going from let’s say fret 3 to 1, that is from a higher numbered fret to a lower one?
Isn’t 12 higher than 1?
Is it ‘down’ to a higher fret since you usually hold the guitar with the head above the body? So if you put your hand at the seventh fret it becomes lower in altitude compared to if you put your hand at the first fret?
What if you sit with the guitar in your lap crossing your legs? Then the tilt could very much be the opposite, the head slightly below the body.
Please create a movie to illustrate what you mean.