You set undo levels independently for Fred4 and for Ted4. This is per user preference.

The default setting may be insufficient.

On Pages main tab in Fred4

On the Edit menu, click Preferences, and then on the Main tab of the Fred4 Preferences dialog, under Number of undo levels, specify what you want. The recommended value may be 400 to 800.

On Articles main tab in Ted4 or in Fred4

On the Edit menu, click Preferences, and then on the Main tab of the Ted4 Preferences dialog, under Number of undo levels, specify what you want. The recommended value may be 200 to 400.