To make sure that the performance of the program does not deteriorate as a result of adding an excessive number of children to a single knowledge tree node, SuperMemo provides a user-defined parameter Tools : Options : Appending : Children limit per contents node. By setting this value, you can make sure that SuperMemo will warn you each time you exceed the determined limit (you can set it anywhere between 1 and 1000). It seems sensible to never add more than a pageful of items to a node for easy review in the contents window. Therefore you are most likely to set the children limit to 10-60.

When you choose one of the appending options (e.g. Edit : Add a new item), SuperMemo will check the number of children at the current category hook and display Category Change dialog box to let you choose the new category hook or let SuperMemo determine the new hook automatically.

In the Category Change dialog box you can choose one of the following:

• OK - to let SuperMemo choose the new hook node automatically. The new node hook will naturally be a descendant of the category root as determined by Tools : Categories
• Change limit - to change the children limit per knowledge tree node
• Select node - to manually choose the new hook node in the contents window (by choosing Make hook on the context menu)

If you always want SuperMemo to choose the new node hook automatically, you can tick the check-box Do not show this dialog box.

If you opt for automatic selection of the new hook of the current category, you should know that you can choose between two modes of selecting the new hook:

• selecting the new hook at the sparsiest location among the descendants of the current category's root (Tools : Options : Appending : Automatic category hook node change : To sparsiest branches)
• selecting the new hook at the last branch of the current category's root that does not exceed the children limit (Tools : Options : Appending : Automatic category hook node change : To terminal branches)