Hi pollock. There will be a number of alternatives here, this is my suggestion:
"I am a qualified Graphic Artist with extensive knowledge in the related fields and would be interested in working in a gallery environment."
I didn't see the above posts so yes I agree your use of knowledgeable was acceptable. I just thought to provide an alternative.
I was talking to a native speaker, there were 4 people talking. D is a man who has a very strange English name “Rorschach”, and I know nothing about this name. Then the native speaker told me something about it, but since I knew nothing about the name, I didn’t know what he was talking about. Then I looked up the name and immediately understood what the native speaker was talking. I wonder if I can say:
Brian, you are knowledgeable.
I want to say that he knows many things. Since “Rorschach” is a name applied to one of the characters of a Chinese cartoon. But he even told me the name is also about a test, which was totally unknown to me.
I think it’s fine. But I looked up “knowledgeable”, I found that the meaning of it is not what I want, so I’m confused.
Brain, you are knowledgeable.
Brain, you are a knowledgeable person.
Does it need to be placed before the noun?
Secondly, I don't know whether "knowledgeable" is fine to mean "full of knowledge", "knows many things". When I was in middle school, my teacher told me "when you see a word with "able" as the suffix, it means "be able to", for example, "doable"="be able to do", "believable"="be able to believe", etc.
If "knowledgeable"="be able to knowledge", it makes no sense here.
Our dictionary has definitions for suffixes and prefixes as well as for whole words. Under -able, there are two meanings. One is the one your teacher gave you, "to be able capable of, to be suitable for", such as enjoyable, or washable.
inclined to; given to; able to; causing: comfortable, reasonable, variable
Someone who is knowledgeable is given to [=in the habit of] knowing.
As for the position:
Knowledgeable can come after a verb, as in "Brian, you are knowledgeable."
In my experience, when we do this, we are more likely to modify knowledgeable in some way.
Brian, you are very knowledgeable. Brian, you are knowledgeable about cars. What do you think of the newest models?
This is not a grammatical rule: this is just a comment on usage.
Note: For second example especially, I would probably say "Brian, you know a lot about cars." "Knowledgeable about cars" can sound too formal for ordinary conversation.