Feature request: promote/demote weave level shortcut

Ideal flow:
- select a block of content
- hit cmd+tab or whatever, and all the choice points or gather points increase their weave depth
- hit shift+cmd+tab or whatever, and all the choice points or gather points decrease their weave depth (to a minimum of 1)

The use case is extracting a block of weave content from somewhere and moving it to its own knot, which usually means reducing the weave level of everything inside it.