The undo history let us undo several steps at once. This is similar to repeat last but lets us choose from the undo history what operation we want to repeat. In the edit menu we also find the repeat history command. Therefore, we can not move something in object mode, tab into edit mode and make selections and then repeat the initial move operation.Д«ut as long as we stay in the same mode we can repeat last on any selection. Keep in mind that toggling between edit and object mode is considered an operation and breaks this pattern. This means that we can make an operation and repeat it again on the same selection, or we can select something else and repeat the operation on the new selection. Repeat last does not affect the selection operations. The repeat last operation has the shortcut key 'Shift+R'. If you make any other operation in between the redo stack is empty and no data can be retrieved from it. Redo is only available when an undo operation has just been performed. Their shortcuts are 'Ctrl+Z' for undo and 'Ctrl+Shift+Z' for redo. The obvious operations are undo and redo. All of these operations are available from the edit menu and a few of them has a shortcut key assigned. Now we will take a look at the operations that are related to undo. I find it more useful to keep this setting enabled to have as many operations available for undo as possible. The Object mode changes will not be stored in the undo queue. Without this enabled Blender will only keep the steps in history made in edit mode.

I keep this at 0 to essentially disable the setting and let the 'undo steps' be the limit no matter how much RAM the undo steps use up. I used to keep mine at around 70 steps but I later realized that it does not have such a huge impact on memory usage so now I use 256.

In the memory and limits section you will find 3 settings related to undo.

What is the redo command on blender