Creating a custom palette in keynote 14.4 not working

Since a few updates ago Keynote deleted all the custom palettes I have in my keynote templates, and the usual feature of dragging the colours into the palette has stopped working.

I waited for a couple of updates to see if it was fixed, but it still doesn't work.

I can't be the only one having this issue, but I can't find anything about it. Is anyone else having this issue, or has anyone found another way of customising the palette?

Thanks