Merging groups won't happen, because you can bulk edit channels now.
Go into the group you want to merge.
Check the checkbox next to the channels you want to move into another group.
You can use the "check/uncheck all" checkbox too at the top of the checkboxes.
You can use CTRL+LEFT MOUSE to check a first and a last checkbox to choose all channels between them.
Use the "edit selected channels" to move the channels into another group.
Go into the group you want to merge.
Check the checkbox next to the channels you want to move into another group.
You can use the "check/uncheck all" checkbox too at the top of the checkboxes.
You can use CTRL+LEFT MOUSE to check a first and a last checkbox to choose all channels between them.
Use the "edit selected channels" to move the channels into another group.