There is inconsistent behavior when deleting nodes and importing content. For all test cases below, create some content at the root level in the pages app / website workspace and continue with each case's instructions.

Case 1
Export the node via JCR app
Delete it via JCR app
Re-import it onto the JCR app -> receive “node already exists message”. I then saw on the bottom left corner the path for mgnl:tmpDeleted$Node

[^Case 1.mov]

Case 2
Export the node via JCR app
Delete it via JCR app.
Close the JCR app
Re-open JCR app
Reimport the node -> import success. No error message.

[^Case 2.mov]

Case 3
Export the node
Delete it via JCR app.
Close the JCR app.
Open the JCR tools app
Click the importer tab
Selected the node to upload
Select "website" workspace
Select the “only import if no existing node” option
Click import -> receive “node already exists” message for mgnl:tmpDeleted$Node

This shouldn't happen as the node is deleted already so it shouldn't exist at all and you should be able to import it.

Case 4
Export the node
Delete it via pages app (not JCR app).
Open the JCR app
Import the page node via import button -> import success. No error message

Case 5
Export the node
Delete it via pages app (not JCR app).
Open the JCR tools app
Click on the importer tab
Select the node to upload
Select "website" workspace
Select the “only import if no existing node” option
Click import -> receive “node already exists” message for mgnl:tmpDeleted$Node

Again - this shouldn't happen as the node is deleted already so it shouldn't exist at all and you should be able to import it.

Workaround
Use one of the successful cases above to import content.
Try not to edit nodes directly on the JCR.

Other Notes
This was tested on 6.2.6
Discussion on Slack https://magnolia-cms.slack.com/archives/CKSC4TJQK/p1612423701093000