How to set QoS like tos_sip and 802.1P priority value

I try to find the settings for QoS in the FreePBX webgui, but no luck so far.
I’d like to set the precedence value (tos_sip=cs5) and the 802.1P priority value.

For the tos_sip-value I found the sip_custom_addition.conf. But in the file it’s warned to apply changes directly in the file. So how do I set it?

As for the 802.1P priority value I completely have no clue where to configure this. Any help would be appreciated.
thx in advance