A Research Study Comparing How Well Different Doses of the Medicine NN0519-0130 Lower Blood Sugar in People With Type 2 Diabetes

Inclusion Criteria: * Female of non-childbearing potential, or male. * For United States (US) only: Female of childbearing potential using highly effective non-systemic methods of contraception with low user-dependency and willingness to continue using it through-out the study or male. * Age 18-75 years (both inclusive) at the time of signing the informed consent. * Diagnosed with type 2 diabetes mellitus greater than or equal 180 days before screening. * Stable daily dose(s) more than or equal 90 days before screening of the following antidiabetic drug(s) or combination regimen(s) at effective or maximum tolerated dose as judged by the investigator: metformin with or without sodium-glucose co-transporter 2 (SGLT2) inhibitor. * Glycated haemoglobin (HbA1c) of 7.5-10.0% (58-86 millimoles per moles (mmol/mol)) (both inclusive) as assessed by central laboratory at screening. * Body mass index (BMI) greater than or equal 23.0 kilograms per meter square (kg/m\^2). Exclusion Criteria: * Treatment with any medication for the indication of diabetes or obesity other than stated in the inclusion criteria within 90 days before screening. However, short term insulin treatment for a maximum of 14 consecutive days and prior insulin treatment for gestational diabetes are allowed. * Uncontrolled and potentially unstable diabetic retinopathy or maculopathy. Verified by a fundus examination performed within 90 days before screening or in the period between screening and randomisation. Pharmacological pupil-dilation is a requirement unless using a digital fundus photography camera specified for non-dilated examination. * Known hypoglycaemic unawareness as indicated by the investigator according to Clarke's questionnaire question.