The ‘use as Pattern’ button on the Custom Pattern tab is intended to give a preview when you’re creating a custom pattern. Are you trying to create a custom pattern?
It may be that you’re trying to fill a region or an entire layer with a pattern.
The Fill Tool is the tool to use for that after selecting a pattern using the Fill Pattern ‘Patterns’ tab or the Patterns docker.
To fill an entire layer with a pattern, you can also use a Fill Layer.
The behaviour of a tool can vary a lot depending on the settings in the Tool Options docker.
When you have the 'Fill Patterns selector widget open, it will have focus.
If you then click anywhere else, that will have the effect of changing the focus e.g to the canvas if you click on the canvas. It will not result in the selected tool being used.
So, you need to click anywhere and then click on the canvas only once.
This is probably because you don’t have pattern selected as the option in the Tool Options docker:
I’m happy you found the culprit and are able now to do what you had planned to do.
I wish you a nice day, much fun with Krita and always happy painting!
And in case of other issues, feel free to ask here in the forum, we’re happy to help!
I think Krita is a great program, but not that easy to understand! But I definitely intend to learn even more Krita. So, I think I will have to call on you in the future.
You may decide to learn Krita the way I used. I have read all the requests for support here in the forum and tried first to recreate the problems of other users with me, and then, after it was recreated, to work out the solution to those same problems with me. Believe me, you can hardly learn more and faster.
It’s always been that way, and it’s not getting any less. But since no one can learn everything at the same time and all at once, the best strategy has always been to work through things in order as they arrive.
And that’s exactly what I’ve been doing, bit by bit, one after the other, after all, I still want to have something to discover tomorrow.