Add option to merge presets about companion HOT 1 OPEN

I'm open to this, it will need some thought on how best to tackle to avoid annoyance to users familiar with the current flow.

I suspect that this will require us to prompt when dropping a preset over an existing button, to ask what should happen. That prompt should allow for:

1. Replace
2. Merge
3. Cancel

Merge will probably want some checkboxes to ask how to merge it, (replace the style, actions, feedbacks)

I guess it will probably be fine if one side has more steps or duration groups than the other

Some challenges I forsee:

1. I don't know what we can do currently if the button and preset disagree on 'relative delays' or 'progress'.
2. Or if two duration groups disagree on 'while held'
3. what to do about names of steps?

from companion.