The commands are summarized in Table 
.
Table: Sequence Term Slot Editing
If a term cursor is at an element of either a term or a text sequence, then OPEN-SEQ-TO-LEFT and OPEN-SEQ-TO-RIGHT add a new empty slot to the left and right respectively of the cursor. The cursor is left at the new empty slot. On an empty term sequence, the two commands have the same effect; they simply delete the nil sequence term. If a text cursor is in a text sequence, both commands open up an empty term slot at the text cursor, and leave the cursor at the new slot.
With text or term sequences represented by a single term, these commands infer the kind of sequence to create from context. Occasionally with term sequences, more than one kind of sequence is permitted in a given context (for example, in precedence objects) and in such cases you can use explicit term insertion commands to create the sequence. Such ambiguity shouldn't arise with text sequences.
OPEN-SEQ-LEFT-AND-INIT and OPEN-SEQ-RIGHT-AND-INIT are similar, but if there is some obvious term to insert in the opened up slot, then that term is automatically inserted and the cursor is left at an appropriate position in the new term.
If a term cursor is at an empty term slot in a term sequence, the CLOSE-SEQ-TO-LEFT and CLOSE-SEQ-TO-RIGHT commands delete the slot, and then (if possible) move the cursor to the element to the left or right respectively of the slot just deleted. If the term slot is filled with a term, that term is first deleted. If the term slot is in a text sequence, these commands leave a text cursor at the position of the deleted slot.