In the iOS version, go to Hub (the snowflake icon), Utilities, Restore exercise songs.
I don't know about Android.
Here's a playlist containing the 62 tunes that show "exercise" as their composer:
Only those different from what you have "should" import.

Exercises (62)

1. Afro 1 - Exercise
2. Afro 2 - Exercise
3. Ballad 1 - Exercise
4. Ballad 2 - Exercise
5. Ballad 3 - Exercise
6. Ballad 3 1 - Exercise
7. Blues - Bird - Exercise
8. Blues - Jazz - Exercise
9. Blues - Minor - Exercise
10. Blues - Minor Waltz - Exercise
11. Blues - Simple - Exercise
12. Blues - Sus - Exercise
13. Blues - Sus 1 - Exercise
14. Blues - Waltz - Exercise
15. Bossa 1 - Exercise
16. Bossa 2 - Exercise
17. Bossa 3 - Exercise
18. Dominant 7 Workout - Exercise
19. Dominant 7#11 Workout - Exercise
20. Dominant 7alt Workout - Exercise
21. Even 8th's 1 - Exercise
22. Even 8th's 2 - Exercise
23. Even 8th's 3 - Exercise
24. Even 8ths 1 - Exercise
25. Even 8ths 2 - Exercise
26. Even 8ths 3 - Exercise
27. Fast Jazz 1 - Exercise
28. Fast Jazz 2 - Exercise
29. Fast Jazz 3 - Exercise
30. Fast Jazz 3 1 - Exercise
31. II-V-I in 12 Major Keys - Exercise
32. II-V-I in 12 Minor Keys - Exercise
33. II-V-I in 12 Minor Keys 1 - Exercise
34. Jazz Waltz 1 - Exercise
35. Jazz Waltz 2 - Exercise
36. Jazz Waltz 3 - Exercise
37. Medium Jazz 1 - Exercise
38. Medium Jazz 2 - Exercise
39. Medium Jazz 3 - Exercise
40. Modal - Aeolian - Exercise
41. Modal - Aeolian 1 - Exercise
42. Modal - Dorian - Exercise
43. Modal - Dorian 1 - Exercise
44. Modal - Herbs - Exercise
45. Modal - Herbs 1 - Exercise
46. Modal - Lydian - Exercise
47. Modal - Miles - Exercise
48. Odd Meter 11-4 - Exercise
49. Odd Meter 5-4 - Exercise
50. Odd Meter 7-4 - Exercise
51. Odd Meter 7-8 - Exercise
52. Odd Meter 7-8 1 - Exercise
53. Odd Meter 9-4 - Exercise
54. Rhythm Changes - Exercise
55. Rock 1 - Exercise
56. Rock 2 - Exercise
57. Rock 3 - Exercise
58. Tonal Cycle of 4th's in 12 Keys - Exercise
59. Tonal Cycle of 5ths in 12 Keys - Exercise
60. Trane Changes 1 - Exercise
61. Trane Changes 2 - Exercise
62. Trane Changes 3 - Exercise

)BOB