New Group not showing in Master View

[TomL8345]

I have 3 Arches 8 segments of Dumb RGB + Strobes.  Earlier this year I created my models of these units and then created groups, Arch x - consisting of all 8 segments, Arch Strobes - consisting of all the strobes, and Arch All - consisting of Arch groups 1-3 + Arch Strobes.  I now want to add another Group of JUST Arch groups 1-3.
I created a group called Arch Only - cosisting of Arch groups 1-3 and saved it.  I went to add it to Arch All, but it is NOT listed in the Add to Group window.  When I go to the Sequencer tab, it is not listed in Master View, but it is listed in Model/Group Window on the Layout tab.

What set have I missed?  I am using 2017.23 64 bit

[Gilrock]

Models do not get automatically added into sequences.  You need to right click a row heading and select the Edit Display Elements option and drag the new model into the view.

[TomL8345]

I knew I was missing a step to add it to my Views.

Why can't I find the new Group Arch Only in the Add to Group: window when I highlight Arch All on the Layout Tab?

[Gilrock]

I don't have any guesses.