Unify saving of events in FTA tree

[blcham]

I have a little trouble saving events in the FTA tree. When I modify a failure rate value, I do not know how to save it. On the other hand i saw once a SAVE button:

We have 2 options to save:

• implicitly when I leave a form field
• explicitly using the SAVE button

A/C:

• decide if use implicit/explicit saving
• implement it consistently in UI