Maybe overthinking it? Really you are just bumping the table to influence the ball. That being said, it is a skill developed over time and if you are a new player you probably just need time to get a feel for it. Play some practice games where you just focus on that skill. Even small bumps at the right time can make a difference. Here’s a couple to work on:

If ball is heading sdtm, bump machine on the side, say, right side, and that will make the ball move a little to the right, and raise the right flipper to deflect the ball.

When the ball hits a sling shot, bump table from the front at the moment it hits the sling to take out some lateral energy from the ball. This tends to make the ball bounce more vertically (lateral movement around the drains is bad, you want to get the ball moving vertically).

https://www.deadflip.com/tutorials

I only have one thing to say about it: just be careful of your hands and wrists because it is easy to overdue it before you know when it is more (or less) appropriate and you will likely feel like doing it often, and those lockdown bars are not kind over time.

I would suggest learning nudging on an EM. It's simpler and easier to learn. Then progress to nudging on a modern game. Nudging on a modern game is more complex and there's so much more you can do. Anytime you are learning a new skill, you want to start with the simple and progress to the more complex. Also, videos can only help you with the concepts. Practicing is the only way to truly learn.

The typical purpose of a forward nudge is give the ball additional vertical momentum. You most often do this when a ball is bouncing off the inlane/outlane post and your desired outcome is bounce the ball upward, then against a playfield obstacle that pushes the ball away from the outlane.

Top level players know when a nudge at the upper part of the playfield is likely to keep the ball out of danger.

Hey there, thanks for the insight!
I asked some professional players on certain nudging moves they just did. Most of the time they couldn`t explain what they did exactly.
I often hear that they are not sure how it affects the ball, but "it seems to work".

The best advice I can give you is that you have to experience the effect of a nudge to understand it, thus using it properly next time.

That means you have to try out different things on the same situation. At one point you will notice a nice effect on the ball and you keep repeating that nudge in that type of situation.
I still have those moments where I learn new applications of nudging (different angle, timing, technique, situation...).
You could start with left/right nudges to get the ball out of the danger zone. That is straight forward and easy to understand.
Step by step you will get better.