I think you need also to edit experience points if you want to be level 20 or what ever. Experience can be edited with Savegame Editor. Here is how much exp point for each level:
Level XP required
1 - 0
2 - 358
3 - 1,241
4 - 2,850
5 - 5,376
6 - 8,997
7 - 13,886
8 - 20,208
9 - 28,126
10 - 37,798
11 - 49,377
12 - 63,016
13 - 78,861
14 - 97,061
15 - 117,757
16 - 141,092
17 - 167,207
18 - 196,238
19 - 228,322
20 - 263,595
21 - 302,190
22 - 344,238
23 - 389,873
24 - 439,222
25 - 492,414
26 - 549,578
27 - 610,840
28 - 676,325
29 - 746,158
30 - 820,463
31 - 899,363
32 - 982,980
33 - 1,071,436
34 - 1,164,850
35 - 1,263,343
36 - 1,367,034
37 - 1,476,041
38 - 1,590,483
39 - 1,710,476
40 - 1,836,137
41 - 1,967,582
42 - 2,104,926
43 - 2,248,285
44 - 2,397,772
45 - 2,553,561
46 - 2,715,586
47 - 2,884,139
48 - 3,059,273
49 - 3,241,098
50 - 3,429,728