For best results, always best to say what version of Premiere Elements that you are using and on what computer operating system it is running.
You have to select them all at the same time, and then Clip Menu/Group.
To select the three, hold down the Shift key of the computer main keyboard and click each content
Or simply, with the mouse cursor draw a rectangle around the clips that you want to select.
The scissors will cut what you have selected. See selection suggestions above.
Any questions or clarification on this, please do not hesitate to ask.
the little scissors do not appear when I try to cut Audio 2 in the same place as Video 1/Audio 1.
The scissors always appear against Video1 regardless of which track is selected, but the cut will apply to the selected track. Alternatively use the shortcut key Ctrl+K.
Insanity is hereditary, you get it from your children.
Let me address your question again as I interpreted it.
You first asked how to group clips.
My answer was to hold down the Shift key of the computer main keyboard and click on each one at a time to select all at the same time.
Then Clip Menu/Group.
Next you asked specifically why you could not cut Audio 2 with the scissors which is now a tab on the stem of the Timeline
Indicator. Let me go into more detail from another approach...
If you have
all not selected and all not grouped and you have the Timeline Indicator at spot "a" and if you use the Timeline Indicator scissors tab or the Ctrl+K keyboard shortcut, you will get a cut at "a" for each of the Audio 2, Video 1, Audio 1 at that spot.
If you do same thing but this time highlight/select ALL of the clips, Audio 2, Video 1, Audio 1, the same thing will happen, that is, cut for each at the same spot.
The only way that I see that you cannot cut Audio 2, is if have an ungrouped situation and you have Video 1 and/or Audio 1 highlighted and Audio 2 is NOT highlighted. In that scenario, the cut will be on the selected clips, Video 1 and/or Audio 1 and not Audio 2.
Once you group the clips, you cannot select one clip without selecting the other two. It is a Group at this point, and the cut will be through all.
As for the Timeline Indicator "scissors" tab...it will look like
barely visible (whether the tracks contents are highlighted or not).
When you bring your mouse cursor over it, it will look like
now the scissors tab very visible whether the tracks contents are highlighted or not.
After all is said and done, the short answer to your question on cutting Audio 2 is....
For ungrouped Audio 2, Video 1, Audio 1
If Video 1 and 2 are already cut
a. place the Timeline Indicator at the place of cut
b. highlight only Audio 2
c. cut Audio 2 with scissors tab on Timeline Indicator or use the Ctrl + K keyboard shortcut.
These have been my observations. Please let us know if they work for you also.