Copy assets between projects

I want to copy some assets form an older project to a new one.
In detail: a cubemap, a model and material I made for the model.

I downloaded all these as a zip and then tried to upload it again.
But uploading failed. It seems that I have to upload all the original hdr files to create the cubemap.

Is it true that I can’t use anything I’ve connected in my old project because thes json files are useless when uploading?

Do I really have to start from scratch? Or did I miss anything?
Please help me with that.

P.S. Forking the whole old project and deleting tons of stuff isn’t a solution.

AFAIK, there is no easy way to copy assets from one project to another.

I thought there was an REST API to upload new assets but is restricted to certain types.

Thanks yaustar

Found this:

Give it a try. The editor and API has changed since then and I don’t think the author is actively maintaining that extension so it may give odd results.