Manage the cursor

The current cursor position is very important for building an expression. At any point, a cursor can have one of the following states:

Locate the cursor before or after a token

The cursor is placed before or after a token, if you click on a spot.

Once you click on an available spot, the cursor is available there. You can perform the following operations:

Delete the Left token or special operator by clicking the Backspace button or key.
Delete the Right token or special operator by clicking the Delete button or key.
Move to the next/previous available spot by clicking the Right/Left key.
Insert a token at the cursor position. In this case, the cursor moves to the spot after the inserted token.
Start typing with any non-special symbol or space. See Direct entry.

You are able to type at the cursor position while the cursor is outside of a token.

If you type any special operator, it has the same effect as clicking the special operator button. The cursor remains after the entered token.
In all other cases, after the first non-special symbol is typed, an input field occurs, allowing to type and edit a string.
The input field goes on top of the existing expression. Once the field is converted into a token, the layout of the expression is recalculated.
Once you press Enter or change the focus from the input field, a new token is created and the cursor is placed after it.

If you click a token directly, the token is selected.

If the token is a direct entry, it converts into the input field after a double-click as shown in the Direct entry.
The token appears underlined.
If the token is collapsed, it is expanded.

If you click on the empty space of the editor (inside the Expression panel):

You can click Tab or Alt+Tab to move around the available cursor positions in the order of the token and subtokens.