"Learnt ins and outs" means acquiring knowledge and mastery of something. Here are some synonyms for this commonly used phrase:
1. Mastered the nuances
2. Learned the ropes
3. Became an expert
4. Acquired proficiency
5. Got the hang of it
6. Achieved mastery
7. Developed expertise
8. Gained insight
9. Became well-versed
10. Became competent
Using any of these synonyms can bring variety and freshness to your writing and communication, while still conveying the same meaning. It can also help avoid repetition, making your message clearer and more effective.