As you have already discovered, it is not possible to vary the trunk IDs from Trk1, Trk2, etc.
However, you can name the interfaces that make up trunk. So when you view the trunks, you can see the interface names too.
interface B1
name "bvenc01 switcha uplink"
no power-over-ethernet
untagged vlan 1
trunk trk1 trunk
exit
interface B2
name "bvenc01 switcha uplink"
no power-over-ethernet
untagged vlan 1
trunk trk1 trunk
exit
core01# sh trunks
Load Balancing Method: L4-based, L2-based if non-IP traffic
Port | Name Type | Group Type
---- + -------------------------------- --------- + ------ --------
B1 | bvenc01 switcha uplink 100/1000T | Trk1 Trunk
B2 | bvenc01 switcha uplink 100/1000T | Trk1 Trunk
B3 | bvenc01 switchb uplink 100/1000T | Trk2 Trunk
B4 | bvenc01 switchb uplink 100/1000T | Trk2 Trunk