The geometry has an attribute “id” which contains string values for each polygon.

How shall I refer to it in the “filter by expression” option in the delete node?

I tried the following, and they didn't seem to work:

Hey Oat,

one way is using a partition node and convert your id string to groups by typing id into the rule field. After that you can delete by group in the delete node.
But I guess there are other ways.

Cheers
CYTE

in Delete SOP expression you may need to use this

however you can use Blast SOP instead and in Group parameter type:

Thank you, tamte. Both of your suggestions work like charms.

I'm glad that I learned a new trick from you.