How to change default import directory from "My Pictures" to somewhere else?

Some how I think a few lost track of the question the OP posted. The OP wants to place images in a folder other than "My Pictures", This is LR 101 basic stuff.

When in the Import screen, notice upper top right  (The To )

Click on that area, and

Click Other Destination, and

Go and pick one, even create one.

Alternatively, over in the Destination Panel, you can specify as well:

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Now that being said, Before import, consider creating this folder you want by adding a folder, and any sub folders.Some people find that logic a bit better, than creating it upon import.

Now, go and watch:Lightroom CC - Importing Images From a Camera - YouTube   Mind you she does not address the To section, (non My Pictures already created)

=And this may be helpful: How to create and manage folders in Photoshop Lightroom Classic CC

You should be able to do that via an import preset. Next time you specify the folder to receive images create a new import preset (located at the bottom of the import dialog).

As far as I know, you have to specify the directory every time you import images.

WW