What I am trying to do is bring a large number of lights slowly to a preset brightness level.
Thing is, I have zero idea or control over what they are BEFORE I start to make my changes.
Using "Fade", it will "pop" everything to 100% then fade down over time--or the converse. Needless to say, that is quite the undesirable action when you're trying to adjust a set of lamps in a way!!
What I WANT is to be able to, for example, say "Bring the selected lights to xx% brightness over 1 minute"--then, if the lights are DIMMER than that already, they will step UP in brightness to that percentage. AND, if the bulbs are BRIGHTER than that arlready, they will step DOWN in brightness.
So that, at a minute, they will ALL be at the set percentage--and none of them will "jump" in brightness level up front--they'll all just start from their current position.
With voice control, I can't think of a good way to do this--any voice assistants I'm aware of accept a level but not a transition time. However, many devices will accept a transition time with a "Set Level" command. A 60-second time might be a bit longer than many devices support, but I don't know off the top of my head what typical ranges are here. You could certainly experiment with your specific device: just go to the device page from the "Devices" list in the admin UI, and look at the "Set Level" command--it accepts two arguments, one for your desired destination level (0-100, sometimes 0-99 for Z-Wave) and transition time (in seconds).
If you always want a specific destination level and a specific transition time, you could crate a virtual switch, tell your voice assistant to turn that on, and have a rule/app triggered by that switch that does a "Set Level" on your device with a specific level and transition time. I suppose you could also create a few such switches for other levels or transition times, though it's likely to get a bit messy if you have a bunch. It may also be a bit awkward on the voice assistant side, too, but you may be able to mitigate that by creating a "routine" (in that assistant's app/website) that responds to more natural speech to perform that action. This is just the only thing I can think of if you want to do this by voice since I'm not aware of any easy way to get the transition time into an arbitrary voice command.
Ah, well, then ignore the struggles I mentioned for getting this to work with voice--you've got an easier time with rules triggered however you want. (Getting an arbitrary transition time would still be hard, but I imagine you could do that with a variable if you don't want to directly specify it in the rule, then manipulate that variable however you want via whatever means.)
The Rule action that will do a "Set Level" with a specified transition time is under "Set Dimmers and Bulbs" and is just "Set Dimmer Level," which allows you to put in both the desired level and (optional) transition time. But again, I'd test this by manually trying "Set Level" on the device page to make sure your device accepts a transition time of 60 or whatever you want. If it doesn't, you may have to resort to the "Fade dimmer over time" action, which will send a series of repeat "Set Level" commands to fake a similar behavior and also eventually reach the desired level.