Reforestation, Nurseries, and Genetic Resources Support Act of 2023 or the RNGR Support Act of 2023 This bill provides statutory authority for the Reforestation, Nurseries, and Genetics Resources (RNGR) program of the Forest Service. Under the program, (1) the Forest Service must provide assistance in supporting nurseries or seed orchards for trees or native plants, and (2) the Department of Agriculture (USDA) must establish a grant program to support of nurseries and seed orchards. Among other requirements, the bill directs the Forest Service to partner with federal and state agencies, Indian Tribes, and private nurseries to provide training, technical assistance, and research to nursery and tree establishment programs that support natural regeneration, reforestation, agroforestry, and afforestation; and expand climate-informed reforestation supply chains through science and research, seed collection and storage, and nursery infrastructure and operations. Under the grant program, USDA may make grants to state forestry agencies, Indian tribes, and certain private nurseries for projects that provide certain infrastructure for seeds and seedlings, establish or expand nurseries or seed orchards, develop or implement quality control measures at nurseries or seed orchards, promote workforce development within any facet of the reforestation pipeline, or carry out certain other appropriate activities.