Possibility to have effect per row

[TME]

If I put Row Probabiity on row 3 at 50%
and I put Row Probabiity on row 4 at 100%

There is 50% chance that my row 4 is ignored, and so the probability of the row 3 will stay active for the next rows.

You are talking about a feature which is not in the current firmware. Indeed, row probability is a special one and if you enable it the chance is there that it doesn't get reset at the next step.

But all other probabilities can be programmed well like this. And then it is maybe the better option to use probability on one of the destinations instead of the row and you can turn them on and off from a safe FX.

And just for the practical use if you could do that:
175 patterns with each 64 rows, where in the menus do you want to set pattern 76 on row 6 to start the effect and row 7 to stop the effect...and that on many patterns on different rows? I know that is not an option.

One option i am actually thinking of while writing this is to exclude always the last FX (in a modular/cv track would be FX4 for example) from the row probability. In that case you could always turn it on or off from FX4 but leave all other parts within the probability on demand. Just an idea and i got to think about the impact.

Seconding the FX4 idea mentioned here, or some other resolution. The current implementation of PROW has severe consequences if the row contains data for a rare event that contains several FX. For example, try PROW001, which can effectively mute the entire track indefinitely (including break points). 

PROW is certainly a special case... An alternative solution to the FX4 idea would be to introduce a new FX (or class of effects) for 'Instances'. For example, PRWI would invokes a single instance of the Row Probability effect that reverts to it's previous value on the following step (or the value resulting from FX called in the subsequent step).