In current beta version (r99) and since the couple of previous beta versions :
Image editor: now allows multiple selection of collision poly points (hold control or shift while selecting), a new 'Select all' option, and dragging multiple points at once.
To add a point you have to double click a collision point, to delete, you have to select a point and press the "del" key.
For both actions a right click on a collision point allows to do it to.
(adding and delete were already in before r97).
04> A field is available since r97.
05> Right-click "Apply to whole animation" is a way to do this.
Also, remember you shouldn't have more than 8 points to make your collision mask anyway (more points might end up in a buggy collision detection and performances loss).