Not as formal as a blazer, not as casual as a cardie, what am I looking for?

[LucyAnnPan]

A denim jacket maybe?
for over a dress or jeans and top to give a bit of warm but not too dresssed up or down.

leather or pleather biker jacket

A shacket? It's like a cross between a shirt and a jacket or a coatigan, a cross between a cardigan and a coat

Personally I think a dënim jacket is often more casual than some cardigans.

Bomber jacket?

https://www.whistles.com/product/jersey-jacket-41835.html

A bomber jacket.

I have denim and biker jackets ...

A knitted jacket. Found one at landsend

A shawl collar blazer in a lightweight material? I have a couple of blazers like this and the no collar/not stiff material combo makes it more relaxed.

Satin bomber jacket?

Long, lightweight ‘duster’ coat?

These are ‘cover ups’ I sometimes wear instead of a blazer or cardi.

I agree about bomber jackets but they are all so short this year?

https://www.thecode.co.uk/product/purple-check-wide-collar-jacket-pvg_028iapt9hds91y?size=m%2Fl&country=GB&utm_source=google&utm_medium=cpc&utm_campaign=24411389018&utm_content=829992387482&utm_term=&ltschannel=MPX-WOMENS-BESTSELLERS-MAXCLICK&gad_source=4&gad_campaignid=24411389018&gbraid=0AAAAADisYDtztqwSD-Jj-gVsMx3He9aUE&gclid=EAIaIQobChMIlfGA2bzilwMVMZdQBh0g4wrWEAQYASABEgKRA_D_BwE