To check which layer a sequence is on, use the Select Objects tool. Type in the name of the sequence and it will show up as an entity (type: "Sequence").
Note: Entities on hidden or frozen layers won't be found by this search. If you can't find the sequence entity this way, unhide and unfreeze all layers.
If the above requirements are fulfilled, you can use the following methods to create or edit position and rotation keys.
Simply use the gizmo to position and rotate the object. This will automatically write keys at the current position of the slider.
Double-clicking a key will display the Key Properties dialogue. You can either enter a new value here or use the buttons to increase/decrease the value.
Double-clicking at an empty spot will create a new key (Its value will be determined by the position/rotation the entity has at this point in time.)
The advantage of this method is that some of the requirements above don't apply: The entity doesn't need to be selected, and the Record button also doesn't need to be pressed. It also is the only method that allows to set rotation to values beyond 360° or -360° (to set the following keys, you can also use the other methods again).
The disadvantage is that you can't change the used coordinate system (see the note below).
Note: Track View keys will always use the World coordinate system if the object hasn't been linked; and the Local coordinate system for linked objects.
Use the XYZ property fields at the bottom of the main perspective window. Similar to editing the keys in Track View directly, but for this method the coordinate system can be changed.
Refer to Animating the Camera by Moving the Viewport.
The in/out tangents for each key are set to 0 by default. This results in an animation that won't have an even movement speed, as the entity will slow down and then accelerate again at each key.
To fix this problem, you'll have to set the in/out tangents to "Auto":