Firmware V1.19

[ehr]

I've been using the groove column for simple 2x and /2 clocked patterns...works great.   I recently tried the new track clock command on the effect column to do what I'd been doing with groove and noticed that when using the clock command in the efx column to change the track clock the pattern has to play through once before the change takes effect.   Is this something that is unavoidable?   Maybe I'm missing something or doing it wrong....

The main reason is that this is the only way to stay in sync with everything else. So you can switch while playing to other (even) scales and it would stay synced with the possibility that you as well can switch back to normal clock. If you could do this on the fly, you would directly loose the synchronisation.
The same for the groove indeed, if you edited the groove and the sequencer is passing half waym then your chance it big that it would run out of sync (because thats what is programmed in then).

That makes sense. 

The way I've been using groove column is to double the ticks per step of all the steps in the patterns that I want to play at a /2 speed then press play.   I don't make changes while the pattern plays.   I just thought that putting one clock command on the first step of the pattern would be easier than changing all the groove steps of the pattern.   No worries using groove works good.

But when that track is not playing, the scale changing will take effect directly, pressing start then will start the pattern directly in the chosen scale.

Goove works this way, but SCLK in the effects column doesn't.  It takes effect after the pattern loops around once or on the start of the next pattern if there is a pattern chained after it.