It exposes devices that have capability pushableButton. It then offers as choices the numberOfButtons the device says it has, and the commands on those buttons for which it says it has the capability.
This is contradictory. Why would you select a device that is not controllable, and then why would you need to start again if it isn't controllable?
Not knowing that a device is controllable or not only happens after you select the device. I suppose this came about with Jason's user drivers without the exposed number of buttons. All of the devices using his drivers showed up (fixed now) even though they did not have number of buttons.
Perhaps a clearer way of stating this would be that you can't edit the app and choose another button device to use.
So, you remove that instance of the app. That's not hard to do.
There is always going to be a risk when you choose to use custom drivers that may not comply with the capability definitions of the platform, and then expect them to work correctly with the rest of the platform.
As I went through the devices, I saw that everything that didn't work was related to custom drivers. I respectfully withdraw my request. 
After adding a button controller, you can always go to live logging to see what the buttons are capable of. Try pressed, held and released on all of them to see each buttons function and how they are mapped.
@bravenel I am trying to utilize my old Iris V1 switches and they are showing in BC, but when I choose an action for the button, normally there is a drop down to select pushed, held, etc, but the drop down is tiny, with no wording next to the check box. If I click in this check box, the app closes with an error. Is it possible that something in the driver isn't assigning the button attributes correctly so BC is not able to use it?
you should see numberOfButtons: 1 in the current states in the driver details, if you don't then click save preferences and you should see it...
I had to click the configure button, then it updated. Save preferences didn't change anything, but configure did, then I also clicked save preferences. I then had to delete my BC app and recreate, then the options for the button showed up.
Thanks for your help! The Hubitat team is the best! Have a great weekend!
How do I set this particular color in the button controller? I've tried separate settings for color temperature, and color - using color value (is that the same as hue?) and saturation. My results when setting via button controller ends up nothing like the original color.
Is there a way to control the volume of a Google Home Mini (speech device) in Button Controller-3.0 ?
In Rule Machine it is possible:
In Button Controller-3.0 I only can choose Music player, and the Google Home Mini is not in the list (not a music player)
I think there is a little bit of version skew here. BC 3.0 was retired several months ago, and then brought back. So some things that got added in that interim may be missing, things that show up in RM. I will see if those can't be added into BC 3.0 for next release.
@bravenel I have an ST button and cannot seem to get the push once to turn on lights. Push again to turn off lights. Is that not possible with BC-3? (Trying not to use held/double click). Thanks
This was done when BC was within RM but should be same:
BC still is in RM as well, under Trigger called "Button Device". There are not conditionals in BC, so this has to be done in RM.
Oops, sorry for misinformation. That shows i don't use BC. 
Thank you. Have a nice weekend.
Is there a way to stop, pauze or resume rules in the app Button Controller 3.1? My goal is trying to use as much of the available Apps instead of rule machine.
3.1 removed this ability. I still have some 3.0 versions and here is difference:
3.0:
3.1:
You can get around this via virtual switch and a RM rule is triggered against.
It works when you use button device in rule machine.
I have the feeling they recommend to use the "simple" APP's instead of rule machine but on the other hand they removing functionality in those simply apps and we are forced to use rule machine, strange
Download the Hubitat app
