Hi,

You can import pos_categ_ids by separating ",".  I will share with you a demo template that I used to import.

Hope it helps

try those steps for fix

1-Make sure your pos_categ_ids/id column has the correct format. Odoo typically expects multiple values to be separated by a comma (,) or sometimes a semicolon (;), depending on your system configuration.

"External ID", "Name", "pos_categ_ids/id"

"prod_001", "Product A", "pos_category_1,pos_category_2"

"prod_002", "Product B", "pos_category_3"

2-Before importing, double-check that the categories you’re referencing already exist in the POS Categories section of Odoo.

3-If using a comma , doesn’t work, try using a semicolon ; instead

4-When importing, Odoo allows linking categories by:

• Name (pos_categ_ids/name)
• External ID (pos_categ_ids/id)
• Database ID (pos_categ_ids/.id)

If you’re using External ID, make sure the values match exactly with the category's external ID in Odoo.