The AVR amplifier can be connected to the TV via an HDMI ARC connection, if the TV has this, or with a Toslink cable.

As I understand it, however, the Bose system is a stand-alone system that does not require an additional amplifier.

Is the idea to connect the Bose system with additional boxes to the AVR-x1400H and combine them? If yes: unfortunately this is not possible.

If only the Bose system is to be connected to the amplifier, this could be done via the headphone socket (note: this has a 6.3mm input). In this case, however, all other outputs are switched off. However, this makes no sense because the Denon AVR would be superfluous and you could also connect the Bose system directly to the TV.

Thank you very much for the detailed answer.