The theological "triage" idea and terminology may be unique to Albert Mohler. But over the years different folks have posited similar ideas about arranging "categories of truth". Here are three.
Categories of Truth We Teach and Preach by David Innes (pastor of Hamilton Square Baptist Church, San Francisco):
Very Clear: To deny these truths is to deny the meaning of words. Such doctrines would include: the Virgin Birth, the Blood Atonement, the Bodily Resurrection, the Deity of Christ, etc.
Logical Conclusions: These truths are drawn by inference from Category 1. Such truths would include: Immersion=Baptism, anything else is just getting wet; the form of church government congregational vs. presbyterian; standards in music, etc.
Informed and Uninformed opinions: Such matters come from one's own personal walk and study. These would include the Textual questions, Sunday Schools, Head Covering for Women, etc.
Personal preferences: Such matters would include: robed choirs, church dinners, etc.
Walter Martin, adapted slightly by someone else:
Essential: These are things that if you deny, you're not Christian. These are things such as monotheism, diety of Christ, virgin birth, bodily resurrection, etc. (roughly the "very clear" above).
Very Important: These might be called "aberrant" if they are denied, and would include things that if denied, would not necessarily qualify as a heresy, but would likely prevent us from keeping fellowship.
Peripheral: personal preferences; e.g. Choir robes, etc.
"Die, Fight, Fuss". There are some things we should die for and some we should fight about. Then there are some that we might fuss about, but we certainly wouldn't die for or fight for them.