Have a Craft with a large Vizzy program. In my case, I edited in about a megabyte of list data for pixel colors. Make changes to the vizzy program and watch RAM usage increase by several gigabytes. This makes the game have a slow input response until exited and restarted.
Note: Although not to this extent, this is observable in normal gameplay, and some past complaints may be related to it. Limiting the amount of data dedicated to the historic log may be wise, both in the designer, vizzy, and planet studio. User-defined thresholds could make sense too, even if not shown in settings and only accessible through XML settings tweaks.
.
Sharing the threshold may be dangerous because of vizzy edits getting rid of the entire craft edit history. Doing an erase when leaving the specific editor would be justifiable.