is it possible to add an option to search for lost characters in the private key?
For example:
Address 1HZwkjkeaoZfTSaJxDw6aKkxp45agDiEzN
Private key 5KYZdUEo***3FPrtuX2Qb***nNP5zTd7yyr2S******sBCnWjss or e3b0c44****c1c149afbf4c8996fb****7ae41e4649b934c****991b7852b855
Maybe someone knows similar already existing programs?
If you have missing characters in WIF, decoding to private key (hex) is not obvious. The most probably the example your show is incorrect.
For restoring WIF, you have several programs, I will mention mine (
https://github.com/PawelGorny/WifSolver) where you may specify "gaps" and characters which you want to try there.
For restoring private key with gaps, I do not know any program, but if you have serious case to solve, I may write something new. All depends on number of missing characters. 12 like in your example is already a serious amount of work.