Seedlings for Sustainable Habitat Restoration Act of 2023 This bill provides support for the collection and maintenance of native seeds and production of tree seedlings. First, the bill expands the Infrastructure Investment and Jobs Act to allow the Forest Service to enter into contracts, grants, or agreements with state forestry agencies, institutions of higher education, and other entities for the (1) collection and maintenance of native seeds, including material from managed seed orchards; and (2) production of seedlings for revegetation. Second, the bill modifies requirements for forest landscape restoration proposals for funding under the Collaborative Forest Landscape Restoration Program. Specifically, the bill adds institutions of higher education to the list of entities that may provide employment or training opportunities under a proposal and allows the employment or training opportunities to include the collection and maintenance of native seeds for revegetation or the production of seedlings.