Comments like this after approx 4h40min from posting the initial question are not helpful.
This is a user forum, and the time taken to respond to your question will depend on when another member is online and has knowledge of the product you are using.
. . . Movie Maker Soundtrack Edition? . . .
Assuming you mean Music Maker Soundtrack Edition as in your previous 2 posts.
This is an old (2012) limited functionality version of Music Maker and you cannot add more VST's to it - also the product is no longer supported by Magix.
To be able to add VST's you need to upgrade to the full version of Music Maker.
It is actually Music Maker Movie Score Edition (latest editon, I think since it I bouth it about a week ago) but I used the Soundtrack Edition in the past and that is why I thought it is the same name. Nevertheless, I do remember that in the Soundtrack Edition (2012) as you said it was possible to add VST instruments. Since Movie Score Efition is a newer version of that I thought iz will be a better version.
"To be able to add VST's you need to upgrade to the full version of Music Maker."
In Music Maker Movie Score Edition in the Program settings, Folders tab do you have this option
If so then create a new folder in the Magix folder that is in your Documents folder and give it a name eg VSTs, put the new VST's into this folder and then add that folder to Music Maker using the button shown above.
Note: ignore my folder paths - yours will be different to mine - I have a second hard drive installed and all my files are on it.
. . . . What is full version of Music Maker? . . . .
Details of the 'full' version of Music Maker are here.
I already checked that option and I don't have anything under My MP3s. Add VST Plugin path or the other one Reset VST... are both missing in my version. Is there a settings option to change in order to see this?