I would like to suggest avoid leg raises for now, as they can increase intra-abdominal pressure and may worsen the separation or hernia if not well controlled.
Start with low intensity exercises even just standing on one leg and then raising your opposite hand to activate your deep core muscles. Then focus on exercises for transverse abdominis and lumbar stabilizers, such as drawing-in exercises, diaphragmatic breathing, pelvic tilts with heel slides, marching in hook-lying, and pelvic floor (Kegel) exercises. Progress gradually to exercises like modified bridges and quadruped arm/leg movements once you can maintain good core control without abdominal bulging.
Also avoid breath-holding, straining, heavy lifting, or any exercise that causes the abdomen to dome or the hernia to protrude more.
Next Steps
Since you also have an umbilical hernia, it’s best to work with physiotherapist who can assess your diastasis and progress your exercises safely.
Health Tips
If you are wearing a abdominal belt,do not completely rely on it. Maintain good posture, roll onto your side before getting out of bed, avoid constipation and excessive coughing if possible, and exhale during effort instead of holding your breath.