You have a perfect solution in the link in the 2nd post:
What’s up with that spammy bumping?
You cannot have Action Mapping in UMG, widgets handle input very differently. There are ways around it but it’s more involved. Essentially, use the button to trigger a function elsewhere. Or…
Alternatively:
Have the button trigger your Fire function instead of Jump, ofc. So it would be something along the lines of:
Now, both the Action Mapping and the Widget button’s onClick execute the same function.