This requires making changes to STOCK game files. The value you will be changing does not impact gameplay, other than to remove the requirement to go through two boring training missions over to start again.

If you've never looked into the JSON datafiles for BattleTech your going to want to use a full featured text editor like NotePad++ (Microsoft's Notepad will mangle the text alignment horribly).

You will also want to backup any file you manipulate so that if something goes wrong you can revert to the stock files.

Go to \\BATTLETECH\BattleTech_Data\StreamingAssets\data\milestones directory and load up "milestone_003_title_coronation_palace.json" and scroll down to the Results bracket and edit the "value" to 105 (default is 100). Save, load BT, start a new game, watch the intro movie and the first and second training missions are skipped, dropping you back into the cutscenes before the third training mission, Majesty Metals.

Its possible to skip ahead past even that mission too. More details can be found here: https://www.reddit.com/r/BattleTechMods/comments/8f0fq7/if_anyones_interested_ive_figured_out_how_to_skip/

Now they made it easy with a patch.

Nice that the team is responsive.