Positive regulator of Notch signaling, required for activation of NOTCH1 intracellular processing and NOTCH1 localization to the cell membrane. {ECO:0000269|PubMed:27764101, ECO:0000269|PubMed:38016980}. This is the function of TM2D3 (TM2 domain containing 3, Ensembl gene identifier ENSG00000184277).