Your only options are to have them be created the length of the project (the default), or to start at the playhead location (which you can change in Preferences).
To trim quickly, I use keyboard short cuts - e.g., select the group, press shift-O to go to it's outpoint, press down arrow to select the layer, press O to trim it to the playhead.
If the playhead was at the start of the group when you brought in the graphic and you set your prefs, you are now done. 3 keystrokes.