In Octamed there was a button ‘slide’ which would generate a slide from the current line, from the previous note to the next. If I remember rightly there was also a glide button which would generate a glide depending on how far the current line was after the note to the note before that note. I looked everywhere for something similar in Renoise but no luck.
As in most oldern trackers there is still the “glide to specified note” (or portamendo to note) - 5xx in Renoise as described at http://tutorials.renoise.com/wiki/Pattern_Effect_Commands#Effect_Column
I agree that a more simple and direct glide effect would be very nice. Not all of us wants to have a pocked calculator when tracking, calculating ticks and cents.
(The problem is that the playback routine never knows what is on the next line. Something like this would probably need to be scripted. “Glide to next note from cursor position” would be a nice script indeed. I’ll have a go at it.)
I used to love the slide button that would do this:
Before clicking slide:
A-3 ----
E-3 ----
After:
A-3 ----
— -202 ← line slide button clicked on
— -202
— -202
— -202
E-3 ----
Should be scriptable…
What I said? Thanks.
Dunks,
This might help you?
Massive thanks! 
It would be good if that tool worked with VST synths.
Sample commands don’t work with VSTs! (Well a few do but you know…)