The Editing Options in Blender’s User Preferences
The second set of user options in Blender is related to the act of editing objects. As shown here, the most relevant options are as follows:
Undo: The options related to undo are pretty important. Here you can adjust how many steps of undo you have when working in Blender (default is 32), as well as toggle Global Undo on and off. Now, you may be wondering why in the world anyone would ever want to disable the ability to undo a mistake.
The most common answer to this question is performance. Having undo enabled requires more memory from your computer, and each level of undo requires a little bit more. Sometimes, when working with very complex scenes or models, an artist might disable undo to dedicate all the computer’s memory to the current scene rather than the steps used to create it. This decision occurs most when artists work with Blender’s sculpting tools.
Playback: When animating, there are times when you need to start animating before the first frame, such as starting the scene with a character, object, or simulation already in motion. By default, however, Blender doesn’t allow you to work in the Timeline (or any other editor) on frame numbers less than zero. But if you enable the Allow Negative Frames check box, that limitation is removed.
Transform: If you’re migrating to Blender from another 3D suite, or if your primary pointing device is a pressure-sensitive drawing tablet, you may find it difficult to use Blender’s “click to confirm” default behavior when grabbing, scaling, or rotating your selections. If you enable the Release Confirms check box, you may feel more comfortable.