Position changes of glissando lines

Several lines (glissando lines and others) permanently change their position after being placed properly and interfere with other elements, especially with double stops. How can I switch off their automatic placement?
Is there a way to create double glissando lines for harmonic glissandi? (Why does Dorico offer only one line with string touch 4-harmonics?)

What other items are present at the same positions, which might be interfering with Dorico’s positioning calculations?

If you’re moving horizontal lines graphically in Engrave mode to be closer to noteheads, have you made sure that you’re inputting notehead-attached lines in the first instance, using the controls at the top of the Lines panel prior to input?

If text items are present, have you tried disabling their collision avoidance before moving items around?

Thank you for drawing my attention to the various types of lines. This was an issue indeed.

However the creation of touch-4-harmonic glissandi with 2 parallel lines is still tedious. Is there a way to create a double glissando line?