Is it possible?
It would be nice to be able to go from a triplet feel to four on the floor from pattern to pattern.
Yea, you can automate LPB and Ticks per line in the master channel.
ZTxx changes Beats Per Minute (T=Tempo)
ZLxx changes Lines Per Beat
ZKxx changes Ticks Per Row
Nice! Thanks! Still getting used to the Codes. There hard to remember!
You can always refer to the handy FX menu in the Pattern Editor Control Panel:
http://tutorials.renoise.com/wiki/Pattern_Editor#Pattern_Editor_Control_Panel
Would any of these commands do the old ‘shuffle-trick’ like the old trackers? something like this (iirc):
F07
F05
F07
F05
F07
and so on…
or:
F08
F04
F08
F04
F08
for more shuffle.
Euuurrrrmmm… I dunno 
Though, there’s always Groove in the Song Options pane.
this “trick” is out of the concept of “Lines Per Beat + Ticks per Line” which is used by Renoise since 2.0
the so called “speed” parameter which the old trackers used was actually the number of ticks per line, but not in the same way that the current TPL is.
In FastTracker, the ticks were processed at a constant speed, not dependent on the BPM values. Thus, by reducing the number of TPL in a song, you were making a row be processed in less time but also with less precision: at “speed” 3, a row is composed of 3 ticks and then would be processed in 1/20th of a second (60Hz/3), with 3 processing steps; at speed 6, a row is processed in 1/10th of a second and 6 processing steps. That’s the reason for the counter-intuitive effect of a smaller speed value resulting into a faster pattern.
The Renoise 2.0+ TPL is instead consistent and logical. Each row is divided in ticks and the speed of processing is dependant on the BPM values.
As said above, you should use the shuffle parameter for immediate groove, or change BPM (ZTxx) or LPB (ZLxx) for per-line changes