Adding a multiple new records to a table via a single portal

Hi Knowledgable People!

I run a martial arts club and have been busy redesigning my database to include a lot of new features.

Using my limited knowledge, books tutorials and the knowledge on this forum, I have managed to create Invoicing, Roles and a variety of other things that I didn't know how to do previously.

I am now trying to create a Grading Skill Set. This is where multiple techniques or skills are assigned to a Belt level. My problem is that I can't seem to create the Grading Skill Sets the way I want to.

THE PROBLEM

What I am trying to acheive is to create the skill set in the Grading Skill Set layout (which is working!), but add the techniques to the Grading Techniques table via a portal on the Grading Skills Set layout (which is not!). The relationship between the Grading Skill Set table and Grading Technique table allows for record to be created and deleted.

The Grading Skill Set layout is shown in the Grading Skill Set.jpg attached.

The reason for trying to do it this way is so that I don't forget to add a technique to a Skill Set and if I do, I can see that it is missing and create it on the spot. There may be many techniques with the same name appearing in the Grading Techniques table so by adding them this way, I will know which one belongs to which skill set, without accidently adding a technique with the same name from another skill set to this one.

Each technique needs to have its own Primary Key, but, whenever I add a new technique in the portal it assigns the same Primary Key to each technique in that portal. Obviously, this can't happen and I get an error as shown in the Error.jpg attached.

I have clearly missed something along the way and have been pulling my hair our to try and work it out, but to no avail.

BACKGROUND TO THE PROBLEM

I currently have 3 tables:
Grading Rank Levels - Where all of the different ranks (belts) a student can acheive are created

Grading Skill Set - The join table that will pair the Grading Techniques with the Grading Rank Level

Grading Techniques - Where the different techniques that will be performed at each grading level are created

The tables are currently joined as shown in the Relationship.jpg attached.

WHAT AM I MISSING HERE?

Any and all suggestions would be welcomed at this point.

Thanks in advance!