In short: you can’t!
Using the line in port may seem possible, but the only way to get sound from the tv is using the PL ports of it.
On a BV7 these can’t be configured as fixed line-out.
You would run into problems with controlling the volume anyway - certainly nothing for an everyday use.
Maybe you could have a sound output from a scart connection - however, whether that would include all sources of the tv or not, I don’t know (I doubt it).
The best thing is to use the converter that was made for such things = a BeoLink ML/NL Converter.
This would give you the optimal integration with ease of use.
Next best would be to connect the BS Core to an analog L/R input port of the BV7.
The Core can easily be set to fixed line out - you must use a PL/RJ45 to phone R/L cable (please contact a B&O dealer or Steve/SoundsHeavenly).
On the BV you must configure the input port - means assign a button on the remote in order to open for sound playback.
The volume is controlled by the Beo4/via the BV - any other controlling of the Core can be done using the Bang & Olufsen app alternatively using 3rd party apps (Airplay/ChromeCasting/BT).
And - of course - you must connect your BL8000 to the BV again.
P.S.. If you also have the Essence Remote, you can use that as usual....apart from controlling the volume of the Core!
Drawback - you always have to use the Beo4 to turn on the tv.
Note: if you have any ML-linkroom, the sound can be distributed there too.
MM