Specialized metabolites are a structurally diverse group of naturally occurring compounds that facilitate plant–environment interactions. Their synthesis and maintenance in plants is overall a resource‐demanding process that occurs at the expense of growth and reproduction and typically incurs several costs. Evidence emerging on different specialized compounds suggests that they serve multiple auxiliary functions to influence and moderate primary metabolism in plants. These new functionalities enable them to mediate trade‐offs from defenses to growth and also to offset their production and maintenance costs in plants. Recent research on glucosinolates (GSLs), which are specialized metabolites of Brassicales, demonstrates their emerging multifunctionalities to fine‐tune plant growth and development under variable environments. Herein, we present findings from the septennium on individual GSLs and their catabolites (GHPs) per se, that work as mobile signals within plants to mediate precise regulations of their primary physiological functions. Both GSLs and GHPs calibrate growth‐defense trade‐off interactions either synergistically or directly when they function as storage compounds, abiotic stress alleviators, and one‐to‐one regulators of growth pathways in plants. We finally summarize the overall lessons learned from GSLs and GHPs as a model and raise the most pressing questions to address the molecular‐genetic intricacies of specialized metabolite‐based trade‐offs in plants. Summary Statement Specialized metabolites boost fitness and adjust trade‐offs in plants under variable environments. Emerging literature has described novel functions in Brassicales specific glucosinolates and their hydrolysis products that have not received adequate attention so far. These auxiliary functionalities enable them to coordinate and fine‐tune primary aspects of plant growth and development under changing environments. Several adaptive scenarios should back these functional diversities in glucosinolates and their catabolites including their metabolic cost‐effectiveness, novel recycling's, and signaling robustness to timely and spatially optimize fitness outputs in plants.