When cannot use PWM in a Tail/Stop function implemented with one TLD2131-3EP, it is possible to implement the two required levels of current by adjusting the RSET value.
This can be done by placing two resistors in series on the IN_SET pin.

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When the tail operation is active, the two resistors RSET1 and RSET2 set the output current.

When the Stop operation is active, the transistor T1 is active and pulls RSET1 to GND bypassing RSET2.
This way the output current is set only be RSET1.

Find more information on the LITIX Basic+ pages